Nutrition for the Horse
Understanding Nutrition Basics For The Horse
In this section of the website I will not be telling you what brands, or even what to feed your horse, as the availability of different feeds and preferred local feeds varies around the world. I also will not be telling you to feed a standard amount of hay combined with a standard amount of grain or processed feed. This type of advice is readily available on many different social media groups, but does not fully address the actual needs of your individual horse. I will be presenting the basics of what a horse requires through various stages of their life, as well as an overview of nutrient requirements, using information gathered by many equine nutrition specialists and presented as research papers or compiled into the main reference book published by the National Research Council (NRC) Committee entitled “NRC 2007 Nutrient Requirements of Horses”, that is used to develop the extruded feeds developed by feed companies. I myself am also not an equine nutrition specialist as that actually requires a PHD in equine sciences. I will however, be presenting quite a large amount of information that I have learned in my own quest to understand how to best feed my horses to help you on your quest to feed your own horses a properly balanced diet.
Most horse owners believe that they are feeding their horse well if it looks like it is healthy, at a good weight, and has a shiny coat, unfortunately this may not be accurate. It is important to learn how to correctly feed your horse as most horses are undernourished yet overfed with our modern feeding practices. Wild horses often travel 16 km/10 miles per day to find enough forage due to sparse grazing conditions which is far more exercise than our average horse receives when at maintenance or light work. As they wander they also select quite a wide variety of different plants that enable them to have a nutritionally balanced diet that our stabled and pastured horses have no access to. They eat a variety of grasses, weeds, flowers, seeds, fruit, and even some bushes and leaves.
The Equine Digestive System Overview
Everyone understands that horses are herbivores and eat vegetable matter instead of meat like a carnivore or omnivore, but many don’t realize that there are several different types of herbivores as well with a variety of specialized digestive systems. Humans, dogs, and pigs are known as monogastric as they have a single chambered stomach that digests food by the use of acids and enzymes prior to it entering the intestines, this is also known as a pre-caecal digestive system. Monogastric systems are designed to digest high levels of concentrates that are low in fiber like grains. Ruminants like cows, sheep, deer and goats have a multi-chambered stomach that has the microbial breakdown and fermentation of fibrous foods at the beginning of the gastrointestinal tract. They are known as foregut fermenters. This allows for the efficient absorption of nutrients along the entire length of the intestines. Ruminant systems are designed to digest high levels of roughages like grass and twigs, and low levels of concentrates. Horses along with rabbits, guinea pigs, and hamsters, belong to the group known as pseudo-ruminants. Horses as pseudo-ruminants, have a monogastric stomach that uses hydrochloric acid and enzymes to digest concentrates like a monogastric animal and also an enlarged cecum after the stomach and small intestine to ferment fibrous materials with microbes like the rumen of a cow. They are known as hindgut fermenters. As a hindgut fermenter a horse can digest more non-structural carbohydrates than a ruminant and more structural carbohydrates than a monogastric feeder. However a fine balance must be maintained to ensure the balance of the systems two components is maintained.
Horses only produce saliva while chewing so providing feeds that require extended chewing helps to maintain gastric health by protecting the upper stomach from acid in the lower stomach. 1ml (1/5th tsp) of saliva is produced for each chew and forages produce over 4 times more chews than concentrated feeds like grain or extruded feeds. Horses will produce between 20-80 litres/5.3-21.1 gallons of saliva per day. An average horse will generally take 60,000 multi directional jaw sweeps (chews) per day when grazing. This amount will be dramatically reduced when confined to a stable and large amounts of grain are fed. When eating forages, horses also employ a longer jaw sweep compared to grain and so will have less issues with teeth not wearing evenly. If a horse is dropping feed as it chews then there can be issues with the teeth not wearing evenly. If the teeth wear unevenly then there is a risk of incomplete digestion of the feed as a result of too large of pieces being swallowed, as well as less saliva production. When less saliva is produced the stomach has less protection from ulcers. A horses highly mobile lips are used to sort feeds, and direct the chosen feed towards the front teeth and into the mouth. Horses graze best on grass that is 10-15cm/4-6 inches tall, but can still graze grass that is 2cm/0.75 inch high.
Once swallowing begins, the process becomes automatic. At the back of the mouth and at the beginning of the esophagus is the pharynx, when feed passes this point it is unable to return to the mouth. When the feed reaches the bottom of the esophagus, a ring like sphincter muscle relaxes so the food can pass into the stomach. This sphincter stays closed to keep the stomach contents from flowing back into the esophagus. This muscle in the horse is so strong that the horse is unable to vomit and rid its stomach of undesirable or excessive amounts of feed. A horse breathes solely through its nose and if it were to vomit, the stomach contents would be expelled through the nose, not the mouth, preventing the horse from breathing. Choke is often discussed in relation to the horse, and occurs when feed is lodged in the esophagus, however it is actually quite rare and most instances can be prevented with correct feeding practices.
The horse’s stomach comprises 8-10% of its gastrointestinal tract, with the adult horse’s stomach volume consisting of approximately 12-15Litres/3-4 gallons. The stomach will empty at a variable rate from 15 minutes to 24 hours depending on the volume of feed ingested, with the average range of time for feed to remain in the stomach being 1-6 hours. Glands in the stomach lining produce hydrochloric acid, mucus, and enzymes to break down food which is then mixed with the feed and any liquids. Stomach acids are produced continuously regardless of whether the horse is eating or not. A horse’s stomach has very few tension receptors to create the feeling of being full, so the horse has a high risk of gorging to the point of causing the stomach to burst. Care must be taken to provide multiple small meals to prevent this. In general, a horse ins unable to vomit due to the strong sphincter muscle between the esophagus and stomach, however in the few extremely rare cases of a horse vomiting it is a veterinary emergency as a ruptured stomach may be the cause. No more than 2.25kg/5lbs of concentrate should be fed at any one time.
Stomach acid is needed to release calcium from the ingested fibre so that it can be absorbed in the small intestine. Free calcium in the stomach also acts as a protection buffer for stomach acid before the food moves into the small intestine. Enzymes produced in the horse stomach digest non-structural carbohydrates in feed. Non-structural carbohydrates consist of simple sugars, and internal cell components that can be broken down by those enzymes. Some examples of non-structural carbohydrates are glucose, fructose, lactose, sucrose, and starch. The stomach and the small intestines are often referred to as the foregut.
The horse’s small intestine is roughly 30% of the gastrointestinal tract, and is 18-20m/60-65 feet long, and can hold 68Litres/18 gallons. Feed will remain in the small intestine for roughly 2-4 hours. The small intestine moves water from the bloodstream to makes digestive juice, which mixes with bile and pancreatic juice to finish the breakdown of proteins, non-structural carbohydrates, and fats. The walls of the small intestine then reabsorb water and the digested nutrients into the bloodstream. Anything that isn’t fibre, such as the cell content can be easily digested and immediately absorbed in the small intestine. Vitamins, calcium, and non-structural carbohydrates such as grains are mostly absorbed in the small intestine.
Feed will reach the cecum 2-6 hours after the horse eats. The horse’s cecum is about 15% of the gastrointestinal tract, and is about 1.2 m/4 feet long, and can hold 23-30 liter/6-8 gallons, this is the first stage of significant fermentation. It forms a blind ended bag, with the end of the small intestine and the beginning of the large intestine forming a “T” shaped top portion. These two portions of the intestines are approximately 5cm/2 inches apart so are at risk for impaction colics; if the cecum is partially empty, which would occur if the horse is not fed enough forages then there is the risk of a torsion colic. It is very important to ensure the horse receives adequate amounts of water and that feeds are changed slowly over a recommended three week period. It takes approximately 7 hours for feed to ferment in the cecum and then be expelled into the large intestine. Microbial fermentation produces vitamin K, B group vitamins, volatile fatty acids and bacterial proteins.
Large Intestine/Large Colon
The large intestine is 3-3.6m/10-12 feet long and can hold 86 liters/22.5 gallons of material. This equates to 38% of the digestive tracts total. The large intestine is the main site of fermentation, where microorganisms break down structural carbohydrates and produce vitamin K and the vitamin B complex. Water and the fermented nutrients are absorbed into the bloodstream and provide up to 70% of the horse’s energy requirements. If non-structural carbohydrates from concentrates arrive in the large intestine without having been digested in the small intestine, then what is called starch overload will occur. Starch overload will cause the microbes in the large intestine to change and upset the fermentation process, causing colic, laminitis, and other problems. Starch overload can be prevented by minimizing the amount of concentrates in the diet and feeding less than 2.25kg/5lbs of concentrates at a time. As water is absorbed, the unusable solids continue into the colon and rectum to become feces. It takes one to two days for feed to travel through the large intestine. If a horse is fed low quality roughages that require a longer fermentation time the large intestine can increase in size and the horse will develop a classic “hay belly” appearance.
The small colon and rectum are approximately 3-3.6m/10-12 feet long and contain 16 Litres/4.25 gallons of material. This is about 9% of the gastrointestinal tract. The small colon removes the last of the water and compacts the material into fecal balls which are held in the rectum until they are expelled.
Basic Nutrient Requirements
Water in often not thought about in any great detail when considering the feeding of a horse but is quite critical to its overall health, and should be the first consideration in the formation of a quality diet. A horse will develop fatal complications sooner from a total lack of water than a lack of feed. Water is essential for gastrointestinal health, proper digestive function, and body fluid balance. If a horse does not receive enough water then it can suffer from dehydration and impaction colic. Signs of dehydration include skin tenting, lethargy, depression, and dull eyes. Dehydration will also cause a dry mouth with sticky saliva that causes a corresponding reduction in feed intake.
When a horse eats, both saliva and an increase in production of digestive juices occurs. The fluid for these secretions comes from the horse’s blood plasma, resulting in an overall drop in plasma volume. This decrease in blood plasma volume creates a feeling of thirst. The horse will drink the greatest amount of water roughly 2-3 hours after being fed its forage. A horse will drink 2-4Liters/0.5-1 gallon per 1kg/2.2Lbs of dry matter, and can drink up to 8 liters/2 gallons per 1kg/2.2lbs of dry matter in higher temperatures. This equates to roughly 19-57L/5-15 gallons per day for the average horse. Another way to estimate a horses water requirements is to assume that it will drink an average of 5L/1.32 gal per 100kg/220 lbs of body weight. A total lack of water is more detrimental to a horse than a lack of feed. As one of the few animals that can sweat, a horse’s water consumption can increase by as much as 300% when in heavy work. Additional water can be added to the diet by soaking feed prior to feeding. Water that contains high levels of trace minerals will affect the overall mineral balance in a horses feeding program.
When water is tested, an analysis of many different components can be provided. The main result to look at to determine if water is acceptable for a horse is the total dissolved solids (TDS). Fresh water will have a TDS level of less than 1,500mg/L or PPM (parts per million), Brackish water has TDS levels between 1,500mg/L or PPM and 5,000mg/L or PPM. A horse can tolerate TDS levels up to 6,500mg/L or PPM but ideally should be provided water with less than 3,000-5,000mg/L or PPM. Most human drinking water has less than 500mg/L or PPM of TDS and is often below 200mg/L or PPM. This means that a horse is able to drink water that is unacceptable for a human, but it is very important that the horse has access to quality water to ensure that dehydration does not occur after eating.
In the winter snow will not be adequate to provide enough water for a horse. Snow typically transforms to water at approximately a 10:1 ratio. Therefore a horse would need to consume 10 “buckets” of snow to equal 1 “bucket” of water. The energy (calories) required to melt the snow and warm the water and horse would also increase the amount of feed the horse would require.
Carbohydrates are the main source of energy in a horse’s diet. Forages, grains and grain products are the principal sources of carbohydrates in any feed program. Carbohydrates that are digested in the small intestine will provide more energy that those digested in the large intestine via microbial fermentation.
Forage is ‘the edible parts of plants (other than the separated cereal), which is used as feed for grazing animals or which can be harvested for feeding’ (Fukushima M, et al). Forage varies in nutritional value depending upon what type of fibre it contains (carbohydrates), how much fibre, and how it has been preserved. It is advised that all forages should be tested for nutritional value to determine appropriate levels of all nutrients to ensure adequate amounts are fed. Forage generally consists of pasture grasses, hay, haylage, beet pulp, and chaff. The majority of a horse’s diet should be made up of forage. Horses have evolved to graze 14-16 hours a day, which stresses how important providing enough quality forage should be. It has been determined that a healthy horse needs to eat 2-2.5% of body weight in forage daily, based on dry matter weight. At no time should a horse be fed less than 1% of its body weight in forage daily. A horse offered free choice forage will often overconsume and eat up to 3% of body weight per day. This is a holdover from their wild days where a horse would eat more in the summer when forage was plentiful to gain weight so that they could last through the winter with less forage.
Fibre is defined as ‘lignin and plant polysaccharides (cellulose and hemicellulose) that are not digested by mammalian enzymes’ which make up the plant cell wall. Fibre is considered a structural carbohydrate (SC). Horses have difficulty digesting fibre that contains lots of lignin on their own, so they need microorganisms to ferment the fibre and break it down into substances that the horse can then absorb. In general a horse will digest the cellulose and hemicellulose easier than the lignin component of the forage, so do better with forage that is less coarse and less total stem content. Fibre is fermented in the cecum, and large intestine of the horse. A horse is capable of digesting approximately 40-50% of the cell wall of forage. It is likely that a horse being fed a high proportion of their feed as forage will need a ration balancer or a vitamin/mineral supplement, because the domesticated horse does not have access to the same variety as its wild cousins.
If you are interested in the actual carbohydrate types in fibre more information can be found at www.prognutrition.com
Various forages are compared based on their dry matter (DM) weights. Pasture grass dry matter content is on average 14-20 % DM, so a horse needs to eat significantly more by weight than the equivalent amount by weight of hay. Keep in mind that the bulk amount of pasture grass and hay will be relatively similar. Grasses have the greatest amount of protein and minerals, and the lowest levels of fiber and lignin when there is a high leaf to stem ratio, like what is found in shorter, younger plants. Ideally a horse pasture should contain a mixture of grasses and legumes that grow well under local conditions and can stand close grazing and wear. In Alberta a horse will require 4-6 acres of cultivated pasture or 8-12 acres of native grasses to obtain enough forage for proper nutrition, this will vary in other areas of the world, depending on local growing conditions. Also keep in mind that it is very easy for a horse on full pasture turnout to eat 20%-60% more digestible energy (calories) than is required for a maintenance diet. There are a variety of grasses that should not be fed to horses, in Western Canada it is Alsike clover and Tall Fescue that is normally found to be of the greatest worry.
The structural carbohydrate (SC) content is highest in straw and mature hays. Legume hays like alfalfa are usually lower in structural carbohydrates (SC) and higher in non-structural carbohydrates (NSC) than grass hays. Most dry hay has more than 85 % DM by weight. When grasses are cured into hay the omega-3 fatty acids are lost and may need supplementing. Up to 80% of vitamin A can be lost in hay and a significant amount of vitamin E as well. Care must be taken to ensure that hay does not lose a significant amount of the leafy portion as that is where the majority of protein and energy is stored in the plant.
Common legume hays are alfalfa and clover. Second or third cut alfalfa hay is more desirable than first cut as there is a higher leaf to stem ratio which increases the amount of energy and protein available. Alfalfa may contain blister beetles and has been associated with allergies in the horse.
Common grass hays consist of timothy, brome, coastal bermuda, fescue, and orchard. Oat hay/greenfeed is also used and can be equivalent to good-quality grass hays. Nitrite levels in oat hay should be under 1% for pregnant mares and under 2% for mature horses, Iodized salt also needs to be fed when oat hay is fed. Timothy is good for mature horses but may not have enough energy and protein for the growing horse so is often mixed with alfalfa. Brome is high in nutrients and makes an ideal hay. Orchard grass is not common for horses but is high in energy and protein. Coastal bermuda grass has been associated with impaction colic. Creeping red fescue is not found to be as palatable to horses as other grasses. Sudan grass, sorghum, hybrid Johnson grass, some white clovers, and alsike are not recommended for horses. Hay fields must remain free of toxic plants because some, like ragwort, become palatable to horses when dried yet still remain toxic. Tall fescue and perennial ryegrass has been associated with multiple problems in the pregnant mare. Both the hay yield and quality are reduced when hay is exposed to rain due to leaching and leaf shatter, often up to 50% of its nutritional value is lost. Haylage must be used with caution and vigilance taken to avoid molds, including botulism. Large round hay bales can increase the risk of Botulism. Moldy hay should not be fed to horses as the fungal spores can cause respiratory problems. To prevent mold and heating, hay should be maintained at a moisture content of less than 200g moisture/ kg. Loosely baled hay should be ideally at 180g moisture/kg and densely packed bales should be at 120-140g moisture/kg. Cubed forages should be soaked when fed to help avoid the risk of choke, as often the horse will not chew enough prior to swallowing due to the shorter lengths of the fibre. Soaking hay will reduce the dust and other allergens but soaking for more than 10 minutes will significantly reduce the mineral content. Oat straw can be fed to horses to keep them occupied and help horses needing to lose weight but should not be fed as the sole source of forage.
In North America the fibre remnants from sugar beet extraction are a common filler additive to extruded feeds and are often fed as a fibre filler on their own. Even though this is the case there abound many misunderstandings about it. I hope to rectify some of the confusion surrounding this excellent feed source. Beet pulp contains 15% fibre, which is slightly less than the standard 18% fibre generally required to be acknowledged as a forage. However beet pulp, as well as soy hulls, contain more readily digestible cell wall fibre than other forages, so can be an important addition to a horse’s diet where more forage is required. Because of this, beet pulp can be used to replace up to 50% of a horse’s fibre requirements, based on dry weight if needed. Since beet pulp is digested in the large intestine it does not create a glycemic or insulin response the way feeding concentrates would, as a result it is of great benefit for horses requiring reduced starch and sugar intake like many draft horses. Beet pulp also produces almost as much digestible energy/calories as oats; beet pulp has 1.3Mcal/lb and oats have 1.5Mcal/lb. Soaked beet pulp is one of the best carriers for supplemental vitamins and minerals in your horses diet, the supplements are mixed in with the beet pulp and do not end up left on the bottom of the feed tub.
Concern #1 – Beet pulp is high in sugar – Not completely true. Beet pulp is the fibre remnant from sugar beets. The sugar is pressed from the beets to make refined white sugar. It is in the sugar manufacturer’s best interest to remove as much sugar as possible so the remaining pulp has very little remaining sugar. Sometimes molasses, which is made from corn, is added to improve the taste for horses. Added molasses is less than 3% of the total dry weight, this means that there is 125ml per 4.5kg or 0.5cup per 10lbs of dry beet pulp. Added molasses can be removed by soaking and rinsing the beet pulp if needed, and many manufactures are now not adding molasses.
Concern #2 – Dry beet pulp will cause a horse to choke – Not completely true. The vast majority of a horses feed is eaten dry, and beet pulp is a common additive to processed concentrates. Horses need to chew their food to produce saliva, which aids in swallowing and digestion. Please see above on how a horse’s digestion works. When a horse eats any feed without adequate chewing they risk choking. In general a horse prone to choking would likely choke on other feeds as well. The horse that chokes will take large mouthfuls of feed, known as “bolting” and swallow quickly without chewing much, in a hurry to eat their ration. Soaking beet pulp will increase the moisture content and aid in swallowing if there is not enough chewing. Horses are also less likely to choke on a soft mash than hard pellets. Choking can also be reduced if the horse is fed at ground level, with a flat pan instead of a bucket; adding a few large rocks that the horse has to move around will also slow their eating down. Even if your horse is not prone to choke, I would recommend soaking beet pulp as it is an excellent way to add water to their diet, which will help prevent dehydration and colic.
Concern #3 – Dry beet pulp will suck the water out of a horse’s stomach, swell and cause their stomach to burst or cause colic – Not completely true. While potentially possible, this must have been started by someone who doesn’t understand how the digestive system works. All horse feed is roughly 85-90% dry matter, as is beet pulp. People become concerned when they observe the amount that beet pulp swells in water in a feed bucket, which is quite a substantial amount. 250ml/1 cup of beet pulp weighs 17g/6oz and when soaked with 500ml/2 cups water expands to almost 1.9ltr/6 cups. A horse’s stomach is filled with digestive acid and enzymes not water, which immediately begins breaking down feed consumed into its basic chemical parts. Water is added to the feed in the stomach and small intestine mainly by saliva, and by extracting it from the blood plasma, so beet pulp will swell somewhat, but if you are feeding the correct amounts of feed then there should be no issue with overfilling the stomach. A horse’s stomach will take 15 minutes to 24 hours to fully empty depending on the amount and type of feed provided, meaning that beet pulp will likely be pushed through rather rapidly if fed in large amounts. A horse usually drinks 2-3 hours after the feed is consumed which means that a large part of the beet pulp will already be in the small intestine where water is extracted as part of the digestive process. The added water could cause the beet pulp to swell but the digestive enzymes will already be breaking it down into its chemical components and removing water at the same time. A 550kg/1,100lb horse needs approximately 12.5kg/27.5Lbs of feed per day broken into at least 2 feedings. This would be 6.25kg/13.75Lbs of feed per meal. The maximum amount of beet pulp fed to a horse is half of the total fibre amount or 3.125Kg/6.875Lbs. This works out to roughly 4.5 litres or 18 cups of dry beet pulp per feeding. I think that most people do not feed this amount of beet pulp.
To help prevent choking, or the potential of beet pulp swelling and causing ruptures or impaction colics, it is recommended to soak beet pulp prior to feeding but not mandatory. Soaking will also add extra water that will be an important aid in the total digestive process. Add 2-3 parts water to every 1 part dry beet pulp, and let soak for 1-3 hours. Using warm or hot water will cause the beet pulp to absorb the water faster if required. Do not soak beet pulp for more than 12 hours at a time as bacteria and mold will grow quite rapidly. Adding any grain or extruded feed to the beet pulp will also increase the amount of chewing and will reduce the risk of choke or other potential difficulties.
Wheat bran/ Rice Bran
Bran mashes are quite popular in Europe but not so much in North America. Contrary to popular belief they do not have a true laxative effect. Due to the increased water intake and disruption of hindgut microbes with the use of occasional mashes, there can be a laxative like effect that is actually not beneficial. Bran mashes are very high in phosphorous so can be used as an aid in balancing calcium: phosphorus levels if needed. Vigilance is required to ensure that the correct calcium and phosphorous ration are maintained. Rice bran is high in fat and can be used to provide extra energy/calories, but should be fed at less than 1kg/2.2lbs per day.
In North America we do not generally feed chaff as a fiber extender but I felt that I should mention it as so many people worldwide do. Chaff or chopped straw is commonly fed to horses to prevent them eating too quickly, and to add filler fiber to their grain or concentrated feed. Chaff not only provides forage but also encourages chewing. If you are feeding straw as a filler or chaff it is advisable to use oat straw and avoid wheat straw as it has too much silica for horses.
Grain/ Extruded feeds/ Concentrates
All forms of concentrate should be measured by weight and not volume when feeding as there can be significant differences in weight when measured by volume. These various grains and concentrates added to a horse’s diet are considered non-structural carbohydrates (NSC) and consist of simple sugars and starches, or components that can be broken down by enzymes produced by the horse in its stomach or small intestine. A general rule of thumb is that the lower the cell wall portion of a feed, the higher the non-structural carbohydrate and energy density of a feed will be. Horses will digest over 95% of the non-structural carbohydrates in a feed. Traditionally oats have been the grain of choice to feed horses in the last few hundred years, followed closely by barley. Corn is also fed but has a significantly higher amount of starches (sugars) than oats, and will travel through the small intestine without full digestion, causing potential disruption in the large intestine. Nutrition research has determined that oats are more digestible by the horse than either barley or corn.
Extruded feeds have recently replaced oats as the major addition to a horse’s base forage for a variety of reasons. The process of cooking an extruded feed improves digestibility and creates higher absorption of all nutrients in the feed including fibre, starch, minerals, proteins, and fats, resulting in less risk of colic. Extruded feeds are more bulky than grain or sweet feeds, creating a slower eating rate and less bolting of food. Slower eating produces more chewing and desired saliva production, which leads to the prevention of gastric ulcers. The nutrients in extruded feed are more readily available for absorption in the small intestine which aids in preventing overload of the hindgut thus reducing fermentation and gas problems. Wheat middlings (wheat byproducts), rye, and sorghum may be used in processed feeds as well as oats, corn, and barley. Molasses is often used in processed feeds to reduce dust and to prevent ingredients from separating. You need to feed your chosen feed at the ‘recommended daily feeding rate’ as determined by the manufacturer in order to meet vitamin and mineral requirements. In most cases, this would be up to 50% of a horse’s diet. Horses fed this amount of a high quality feed throughout its life would not be receiving adequate levels of forage to ensure an optimal digestive process. A diet is considered high starch when 30%-50% of the diet is based on grains or extruded feeds. A high starch diet has been found to reduce the amount of digestive bacteria in the cecum and also to raise blood glucose and insulin levels. To prevent excessive weight, it is usual to feed supplemental feed in the required amount to maintain the desired body score after appropriate amounts of forages are provided. This, however will then cause mineral imbalances because the nutritionists who designed the extruded feed balanced the minerals based on the suggested required amount. At no time should more than 0.5% of a horse’s body weight be fed in grains or concentrates at a single feeding, and no more than 50% of the total daily ration. Large meals of concentrates greater than 0.25% body weight should not be fed within one hour prior to, or directly after exercise to reduce the risk of colic or other gastrointestinal upsets.
Ration balancers are packaged supplements generally consisting of protein, vitamins, and minerals. A ration balancer is lower in digestible energy than a traditional grain/concentrate supplement so can be an important addition to a horse’s diet where feeding high levels of concentrates is not desired. Worldwide, ration balancers can come as a pellet or as a loose powder. In Alberta, ration balancers are generally only readily available as a vitamin/mineral powder that is “top-dressed” on a concentrate or beet pulp ration. Manufacturers do produce a pelleted ration balancer that can be purchased if a local supplier is found.
Digestible Energy/ Calories
Digestible energy (DE) is the amount of useable energy in the form of calories that a horse obtains from its feed. Energy supplied by a forage analysis or feed tag will be referred to as Mcal/kg or Mcal/pound. The total daily requirement will be expressed as Mcal. Soaking hay reduces calories but also leaches minerals. The required digestible energy should be obtained through the forage that a horse receives, with concentrates only being used to provide extra energy to maintain a desired weight. When a horse is fed a diet that is predominately forage based they will produce more heat than a horse fed a mixed diet. In cold weather a horse will need an increase in roughage fed for increased heat production rather than an increase in concentrates.
Protein is required by the horse for maintenance, reproduction, lactation, and growth. Protein is also a major component in muscle, hair, skin, vital organs, milk and enzymes. The major source of protein in a horse’s diet is usually supplied by the forage it eats, either pasture grasses or hay. The greatest concentration of protein is found in the leafy part of the plant. Legumes have the highest protein levels, followed by cool season grasses, with warm season grasses having the lowest levels of protein. Protein levels drop as the plant matures so cutting or grazing will maintain a higher protein level as the plant is kept at a younger stage of growth. A forage should be chosen that contains at least 8% protein for a mature horse. Lactating mares, foals, growing youngsters, and senior horses require higher quality protein than an adult horse on a maintenance feeding program. Extremely high amounts of protein to increase a young horses growth rates are not advisable as there is also an increased risk of serious developmental issues that will affect the horse’s future abilities. Protein requirements are actually for the various amino acids that protein breaks down into. Lysine is the only amino acid that has requirements established for the horse at this point. The remaining amino acid requirements can be estimated by following the proportions found in a horse’s muscles, with the following results: Lysine, 100; methionine, 27; threonine, 61; isoleucine, 55; leucine, 107; histidine, 58; phenylalanine,60; valine, 62; arginine, 76; and tryptophan, undetermined. Higher quality proteins can generally be determined by their higher amount of lysine and threonine. However all the other essential amino acids must be in balance as well. When determining protein requirements for the horse, the digestible protein (DP) rather than the crude protein (CP) must be considered even though most protein is listed with its crude protein amounts. Protein is mainly digested in the foregut (stomach and small intestine) rather than the hindgut (cecum and large intestine) so the source of the protein should be considered as well. Quality protein sources are alfalfa, milk-based products (whey), canola meal, and soybean meal. Linseed/flaxseed meal is a popular additive to feeds for shiny coats and weight gain, but does not have an ideal amino acid balance to be considered a quality protein. Excess protein greater that 12% for the adult horse, can result in ulcers and poor digestion as well as a variety of other health issues. Excess protein will pass out in the urine and create an excessive ammonia smell.
Fats and oils are needed to help with the absorption of the fat soluble vitamins A, D, E, and K. Fats are also needed to provide the essential fatty acids omega-3 and omega-6. Pagan et al (1995) found that added fat in the form of vegetable oil can contain up to 3 times as much digestible energy (DE) as oats and up to 2.5 times as much DE as corn. 250ml/1 cup of oil can replace 0.7kg/1.5lbs of concentrates. A horse does not have a gall bladder so is only able to utilize limited amounts of fats. Adding fat to the diet as a substitute for non-structural carbohydrates will reduce the horse’s glycemic response. Research (Pagan et al, 1995) has also shown that adding fat will reduce the blood sugar glycemic response of non-structural carbohydrates by possibly slowing down gastric emptying. Vegetable oils also seem to be digested better than a traditional high grain diet. The best vegetable oils to use for horses are corn, soybean, ground linseed/flaxseed, canola, and rice. The taste of corn oil is the most preferred by horses. The fat in whole grains and oilseeds like flax may not be digested properly in the small intestine unless they are ground prior to use to. Horses benefiting from higher fat in their diet are harder working horses, growing horses, lactating mares, hard keepers, and senior horses. Horses that suffer from Cushings, Insulin Resistance (IR), Polysaccharide Storage Myopathy (PSSM) (tying-up), and Equine Polysaccharide Storage Myopathy (EPSM) will also benefit from added fat. Show horses are often fed linseed/flaxseed oil to aid in the development of a quality hair coat and hoof wall. Proper ratios of omega-3 to omega 6 for a horse is 4:1. Canola, soy and linseed/flaxseed are the only vegetable fats to contain enough omega-3 fatty acids to be beneficial. Canola oil has 11% omega-3 while linseed/flax seed contains 8%. Good sources of omega-6 fatty acids are soy, corn, sunflower, and safflower oils. Unprocessed oils purchased in bulk from a feed store will have higher levels of minerals than oils purchased from a grocery store. Care must be taken when feeding fat however, as a high fat diet can also lead to Insulation Resistance in horses that do not already suffer from it. Added fat in the diet should be less than 10% or 500ml/2cups of the total diet, and is generally under 6% when no extra fat is added. When oils are added to the diet, they must be balanced with appropriate levels of vitamin E to ensure correct absorption. While some benefits of added fat to the diet may be noticed within 3-5 weeks the full benefits may not be noted until closer to 2-3 months.
Vitamins are organic compounds containing carbon atoms that are found in tiny amounts in natural foodstuffs. The NRC 2007 Nutrient Requirements of Horses, states that it is not necessary for most horses on proper forage feeding programs to be fed supplemental vitamins. Most vitamins are manufactured by the microorganisms found in a horse’s cecum and large intestine, or are found in pasture and hay. Fat soluble vitamins can be stored in the body while water soluble vitamins are not. Vitamin E supplementation however, will need to be provided for horses that are fed large quantities of processed feed/hay, and oils/fats, or are on a heavy workload such as horses in race training.
Vitamin E (d-Alpha-Tocopherol)
Vitamin E is a fat soluble vitamin that is absorbed in the small intestine and is generally expressed in International Units (IU). Vitamin E is an antioxidant, useful to the nervous and immune systems. It is not usually added to any commercially formulated mineral mixes as it will rapidly oxidise when stored with other supplementary minerals and be rendered ineffective. Vitamin E is abundant in grass so will not need to be supplemented to horses in maintenance or low work that are fed a mainly pasture forage diet. Studies have shown horses can benefit from vitamin E supplementation when on increased levels of work, or fed a diet consisting mainly of hay. Broodmares and foals have a higher requirement for vitamin E than mature horses. Care must be taken to ensure that excess vitamin E is not provided as it is stored in fat cells until required and so can cause toxicity. Horses can store vitamin E for up to 18 months before needing supplementation. Natural vitamin E (d-alpha tocopherol) is absorbed better than synthetic vitamin E (di-alpha tocopherol). The easiest method to supplement Vitamin E when needed is human liquid Vitamin E capsules. Capsules can be fed in the feed whole, cut up with scissors, or as a last resort, soaked in hot water then added to the feed. As Vitamin E degrades quickly it should be used within six months, stored separately in a tightly closed container, kept away from moisture, sunlight, and heat, and kept away from mineral supplements. A commercial horse Vitamin E supplement in powder or solid form must be mixed with a small amount of oil to aid in the passage of the intestinal wall or it will pass through unabsorbed. Vitamin E is required for proper uptake of selenium. Deficiencies of vitamin E can contribute to ocular (eye) lesions, reproductive failure, Wobblers Syndrome, Equine Degenerative Myeloencephalopathy (EDM), Equine Motor Neuron Disease (EMD/EMND), and Neuroaxonal Dystrophy (NAD). vitamin E deficiencies can also affect the proper absorption of selenium, resulting in the appearance of a selenium deficiency.
Vitamin A (trans-retinol, Beta-carotene)
Vitamin A is a fat soluble vitamin that is absorbed in the small intestine and is generally expressed in International Units (IU). Vitamin A is well known for its role in night vision, and has crucial roles in reproduction, embryo development, and immune responses to infection. Carotenoids, the components in red, yellow, and orange plants are usually converted into vitamin A in the body. Grasses, bright green hays, and grains will proved all the vitamin A required. A 17-20cm (6-8 inch) carrot contain roughly 8500 IU of vitamin A which is about 1/3 of the daily required vitamin A for the mature horse. Care must be taken to ensure that excess vitamin A is not provided as it is stored in fat cells and the liver until required and so can cause toxicity. Excess vitamin A can cause several serious problems, including birth defects (teratogenesis), sloughing of the skin, bone fragility, developmental bone disease in young horses, degenerative arthritis of the spine (hyperostosis), and other abnormal bone deposits. Extremely low levels of vitamin A intake are required before signs of deficiency occur. Vitamin A deficiency can cause night blindness, impaired growth, reduced formation of blood cells, and respiratory infection. Supplementation will only be required if the forage consists of bleached (not green) hay or hay that is more than 12 months old.
Vitamin B1 (Thiamin), Vitamin B2 (Riboflavin), Vitamin B3 (Niacin), Vitamin B5 (Pantothenic Acid), Vitamin B6 (Pyridoxine), Vitamin B7 (Biotin), Vitamin B9 (Folate/Folic Acid), Vitamin B12 (Cobalamin)
The B vitamin complex is mainly manufactured by micro-organisms in the large intestine so does not need to be supplemented. Excesses will be excreted which will simply create expensive horse urine if supplemented, as the B vitamin complex are water soluble vitamins.
Vitamin B1 (Thiamin):
Thiamin is involved with carbohydrate metabolism. It is found in grain, grain byproducts, protein supplements, and brewers yeast. The classic thiamin deficiency is known as beriberi and affects the heart, circulatory system, and nerves. Symptoms of thiamin deficiency can include decreased muscle strength, localized involuntary muscle twitches, loss of muscle coordination, slow heart rate and weight loss.
Vitamin B2 (Riboflavin):
Riboflavin is involved with converting food to energy, antioxidant defense mechanisms, lipid metabolism, and drug metabolism. No deficiencies or excesses have been noted. Horses should have all needs for riboflavin met through a foraged based diet so no supplementation is required.
Vitamin B3 (Niacin):
Niacin is involved with cell signaling, metabolism and the production and repair of DNA. No deficiencies or excesses have been noted. Niacin is produced by microbial fermentation in the cecum and large intestine of the horse so no supplementation is required.
Vitamin B5 (Pantothenic Acid):
B5 is involved with converting food to energy, hormone and cholesterol production. No information is currently available on the requirements of the horse for pantothenic acid. It is produced by microbial fermentation in the cecum and large intestine of the horse so no supplementation is required.
Vitamin B6 (Pyridoxine):
B6 is involved in red blood cell production, amino acid metabolism, and the creation of neurotransmitters. No information is currently available on the requirements of the horse for pyridoxine. It is produced by microbial fermentation in the cecum and large intestine of the horse so no supplementation is required.
Vitamin B7 (Biotin)
Biotin is important in the body for keratin formation in the form of strong hooves and hair, fatty acid synthesis, amino acid metabolism, non-carbohydrate glucose generation, and cholesterol metabolism; it is also essential for cell number increases. Biotin, like all B vitamins, is manufactured by gut microorganisms and is also found in fresh grass. Biotin deficiency symptoms include itchy flaky skin and excessive dandruff. Biotin deficiencies also create multiple hoof related problems that can include soft and crumbling white line, thin friable hoof walls, and cracked or fissured hoof walls. Biotin supplementation can help horses if there is a noted deficiency, and who do not receive enough fresh grazing or during the winter. For a horse that is mainly pasture fed, there is less of a likelihood for a deficiency to be present and even less likely if the horse is fed additional biotin sources such as grains, brans and ground seed meals such as Linseed/flax. No definitive requirements for biotin have been established for the horse.
Vitamin B9 (Folate/ Folic acid):
Folate is involved in the formation of red and white blood cells, amino acid metabolism, cell growth, and proper cell division. Horses treated with microbials for equine protozoal myeloencephalitis (EPM) will have reduced folate concentrations, but should not be supplemented. No information is currently available on the requirements of the horse for folate. It is produced by microbial fermentation in the cecum and large intestine of the horse so no supplementation is required.
Vitamin B12 (Cyanocobalamin):
B12 is vital for DNA production, neurological function, protein synthesis, carbohydrate metabolism, fat metabolism, and red blood cell development. No information is currently available on the requirements of the horse for Cyanocobalamin. It is produced by microbial fermentation in the cecum and large intestine of the horse so no supplementation is required.
Vitamin C (Ascorbic Acid)
Vitamin C is an antioxidant that is required for collagen synthesis, bone calcification, hormone synthesis, antihistamine control, and conversion of vitamin D3 (cholecalciferol) to the Vitamin D metabolite calcitriol. A deficiency of vitamin C may cause a depressed immune system, poor hair coat, delayed healing of wounds, heavy bleeding, deteriorated or enlarged adrenal glands, spinal curvature to the side (scoliosis), and swayback (lordosis). Vitamin C is a water soluble vitamin that is produced by the horse so supplementation is not generally required in the diet.
Vitamin D (Calciferol)
Vitamin D is a fat soluble vitamin that is absorbed in the small intestine and is generally expressed in International Units (IU). It is important in the absorption and mobilization of calcium, and also influences the growth and differentiation of cells. Vitamin D is produced through exposure of the skin to the ultraviolet rays in sunlight; abundant Vitamin D is also found in hay, especially if it is less than one year old. Since vitamin D is important to the proper uptake of calcium, deficiencies will appear the same as a calcium deficiency, with symptoms such as stiffness, lameness, swollen joints, and brittle porous bones. No reports of vitamin D deficiency have been reported in horses that have some exposure to sunlight. Care must be taken to ensure that excess vitamin D is not provided as it is stored in fat cells until required and so can cause toxicity. Too much vitamin D can cause hardening of soft tissues especially of the aorta, hypercalcemia (leaching of calcium from the bones) and death. The upper safe limit of intake is 44 IU/kg of bodyweight. No supplementation is required if the horse spends time outdoors.
Vitamin K (K1/phytonadione, K2/menaquinone)
Vitamin K is a fat soluble vitamin and is generally expressed in International Units (IU). It is produced by intestinal microorganisms and is also found in the forage eaten by the horse. The majority of vitamin K requirements will be provided by the forage eaten. Vitamin K is used by the blood proteins involved in clotting, bone metabolism, and also may inhibit calcification of blood vessel walls. A vitamin K deficiency will cause blood to not clot properly. At this date no diet related deficiency or excess of vitamin K has ever been reported or suspected in horses. No supplementation is required although Vitamin K is often added to the diets of high performance horses to prevent lung bleeds.
Minerals are inorganic compounds that do not contain carbon atoms and must be consumed in the diet to meet required amounts. Horses will receive a large amount of their required minerals from the forage that they eat. It is likely however, due to our modern farming and pasture management practices, that supplementation will be required for horses to grow correctly and be able to perform at their full potential. In North America most horse forage will be deficient in selenium, zinc, copper, and magnesium. Chelated trace minerals are more easily absorbed than the minerals in their inorganic form. A chelated mineral has been combined chemically with amino acids to form “complexes.” Macrominerals are usually measured as grams/Kilogram (g/kg) or percentages (%) of the diet, while microminerals/trace minerals are measured as milligrams/kilogram (mg/kg) or parts per million (ppm). Most minerals must be fed in balance with others to ensure effective absorption, so sometimes an excess of one mineral will present as a deficiency in another. Avoid feeding unbalanced single minerals or supplements with just a few combinations as you will likely not manage to achieve proper overall balance. Mineral supplementation is best achieved through a ration balancer or a powdered trace mineral supplement. A mineral block is generally less than 5% mineral and more than 95% salt. Block licks are designed for cattle that have a rough tongue while horses have a smooth tongue and are unlikely to be able to acquire enough of the minerals through licking.
Selenium is a micromineral and is generally expressed as parts per million or mg/kg as part of the diet. Selenium is required for normal function of the immune system, muscle function, thyroid hormone metabolism, and cell detoxification. This mineral is very important to monitor in your feed program. If a horse receives too much, symptoms include loss of appetite, loss of mane and tail hair, and dry, brittle, cracking hooves, leading up to blindness (blind staggers), head pressing, loss of the hoof wall, paralysis, and ultimately death. Mild symptoms of low levels of toxicity include excess mane and tail dandruff, and cracking of the hooves around the coronary band. A high number of toxicity cases have been a result of inappropriate injections of selenium/vitamin E. If the horse does not receive the required amount there is also serious health problems that can result in deaths caused by nutritional myopathy (white muscle disease), weakness, impaired locomotion, difficulty swallowing, respiratory distress, impaired cardiac function, Equine Motor Neuron Disease (EMD/EMND), Neuroaxonal Dystrophy (NAD), and Equine Degenerative Myeloencephalopathy (EDM). In the brood mare low levels of selenium have been associated with retained placentas, and foals born weak, and with difficulty moving, suckling and swallowing. Most of North America contains low amounts of selenium so horses will potentially not receive enough. In the Canadian praries the alkaline northern grey wooded soils are lower in selenium than the black/brown prairie soils. Drought conditions that cause forages to increase their root depths can contribute to increases in selenium levels. Selenium absorption is affected by vitamin E and must be balanced accordingly. In general, feed and forage will supply around 0.2-0.3 mg/kg (2.2 lbs) of feed. To avoid deficiencies a horse needs a minimum of approximately 1mg per day. Toxicity generally starts around 50-500 mg per day for chronic poisoning and 2500 mg per day for acute.
Calcium is a macromineral and is expressed as a percent or as grams required in the total diet. 99% of all the calcium in the horse’s body is found in the bones and teeth. Calcium is important to the growing horse as a key component for bone mineralization. Bone mineralization is how the bone increases in length, diameter, and strength. Bone mineralization continues until a horse reaches 6 years of age, at which point maximum bone mineral content is reached and the bone stops growing. Bone calcium and mineralization is increased with exercise, and extended stall rest will cause bone loss as a result of disuse and will likely require increased calcium to strengthen the bone once the horse is returned to a pasture setting. Short sprints of less than 82m have proven to be more effective at building bone strength than longer distances at slower speeds in young thoroughbreds; this is because bone mineral deposition is regulated by forces applied to the skeleton. Calcium is also important for the proper function of enzymes, blood clotting, muscles, and nerves. Calcium must be balanced with phosphorous to ensure proper absorption. The calcium to phosphorous ratio (Ca:P) can be tolerated in a range as high as 9:1, but should ideally be in a range from 1:1 to 2:1 for mature horses. Calcium to Phosphorous ratios for growing horses should be 1.5:1 to 3:1. Grass hays will generally fall in this acceptable range but alfalfa hay can be as high as 6:1 or even higher. Vitamin D and magnesium are also important to ensure calcium is absorbed properly. Deficiencies in calcium and phosphorous in the growing horse result in bone deformities (developmental orthotic diseases), big head disease/Millers disease (Osteodystrophia Fibrosa), slow growth, and skeletal weaknesses. Lack of adequate calcium in the diet causes calcium to be removed from bones to provide for metabolic demands and thus causes a weakened skeleton. Excessive calcium can cause spasms, twitching, irritability, and hypersensitivity. The maximum tolerable amount of calcium should be limited to 2% of the diet for all ages of horses. Growing horses should receive approximately 1.2% calcium for reduced risks of Developmental Orthopedic Diseases (DOD).
Phosphorus is a macromineral and is expressed as a percent or as grams required in the total diet. Phosphorous is required to make teeth and bone and is also needed for many energy transfer reactions. Phosphorous must be balanced with calcium at all times or improper absorption of both minerals will occur. The calcium to phosphorous ratio (Ca:P) should ideally be in a range from 1:1 to 2:1. Grass hays will generally fall in this range but alfalfa hay can be as high as 6:1 or even higher. Absorption ability of phosphorous needs to be taken into consideration as well, most phosphorous sources are absorbed at 35% or 45% but can be as low as 25%. Wheat bran and rice bran are high in phosphorous so if fed they must be balanced carefully with the provided forage. It is also possible for forages to contain too high a phosphorous amount. If not enough phosphorous is fed then all the potentially available calcium cannot be absorbed, resulting in reduced bone density and the appearance of a calcium deficiency. Too much phosphorous can also cause problems by pulling calcium from the bones to balance the excessive phosphorous.
Magnesium is a macromineral and is expressed as a percent or as grams required in the total diet. Magnesium is important for the development of the bone collagen matrix and bone mineralization. It is also found in the blood, helps enzymes activate, and facilitates muscle contractions. Good sources of magnesium can be found in alfalfa hay and soybean meal. Absorption rates for magnesium is generally in the 40-60% range with 40% used for determining required amounts. Magnesium deficiency can cause spasms, twitching, irritability, hypersensitivity, and loss of body control. Extreme magnesium deficiency can lead to collapse, breathing issues (hyperpnea), and death. Because of the symptoms of low magnesium an urban myth has been created that feeding extra magnesium is calming, however when a horse has the correct amounts any excess is excreted from the body.
The main electrolyte is sodium, followed by chloride and then in much smaller amounts, potassium, and bicarbonate. Sodium, potassium, and chloride are macrominerals and are expressed as a percent or as grams required in the total diet. Electrolytes are important for the production of bodily fluids, the contraction of skeletal, heart, and smooth muscles, nerve function, transport of a variety of substances across cell membranes, and the maintenance of normal hydration levels. Electrolyte levels in the blood have priority so the body will move electrolytes from other areas to maintain the correct blood concentration levels. This is why it is possible to check electrolyte levels by pinching skin and looking for “tenting” effects. It is possible that dehydration levels as low as 2-3% can reduce a horse’s performance by as much as 10%. Electrolytes are provided in required levels for most horses in their feed with the exception of sodium. A mature horse will require the supplementation of sodium in the form of salt in the amount of 15-30g/1-2Tbs per day, or 0.5-0.7% of the total diet. The absorption rate for sodium has been set at 90% with the maximum acceptable level of sodium in the diet set at 6%, with any excess being excreted in the urine as long as sufficient water is provided. If a horse is exercised heavily for more than 2 hours it will require additional electrolytes to replace those lost in sweat. An endurance race can cause a horse to lose 34.5-46g or more of sodium in a single race due to sweat losses, which is double the daily requirement. Salt can be added directly to feed, syringed into the mouth, or provided via a salt block. Salt blocks in Canada are generally colour coded: plain salt is white, salt with iodine is light red, salt with iodine and cobalt is blue, salt with selenium is yellow brown/tan, and salt with trace minerals is dark red/brown. A salt block will likely not provide enough salt for a horse in work due to the small amount of saliva produced by the licking action as well as the fact that the smooth tongue of a horse is not as efficient as a rough tongued cow. Salt is also the only documented craving that horses have. A deficiency of salt and other electrolytes can cause issues such as muscle cramping, tying up, alkalosis, fatigue, muscle weakness, and diaphragm flutters (Thumps). The first signs of a sodium deficiency may consist of attempts to lick potentially salty objects like tool handles or vehicles, slowed rates of eating, and reduced water intake.
Chlorine is a macromineral and is expressed as a percent or as grams required in the total diet. Chlorine is normally found in the diet as chloride and accompanies sodium in the form of the salt sodium chloride also known as common salt. As an electrolyte, chlorine is important for the production of bodily fluids, the contraction of skeletal, heart, and smooth muscles, nerve function, transport of many substances across cell membranes, and the maintenance of normal hydration levels. On its own chlorine is an essential component of bile and the formation of the hydrochloric acid component of gastric digestion. A chlorine deficiency is unlikely to occur without a corresponding sodium deficiency. A deficiency of chlorine can cause issues such as muscle cramping, tying up, alkalosis, fatigue, muscle weakness, diaphragm flutters (Thumps), decreased feed intake, weight loss, decreased milk production, dehydration, constipation, and an appetite for non-food items.
Potassium is a macromineral and is expressed as a percent or as grams required in the total diet. Potassium is involved in intercellular function and is important in the maintenance of the acid-base balance and cell pressure. Potassium is also involved in the connection between nerves and muscles. Forages and oilseed meals contain 1-2% potassium which greatly exceeds requirements, therefore it is unlikely that potassium will need to be supplemented. An absorption rate for potassium has been proposed at 80% to determine required amounts for adult horses. Growing horses have been assigned an absorption rate of 50% to ensure adequate amounts of potassium. Horses in heavy work that sweat a great deal may require potassium supplementation as potassium is considered an electrolyte. A potassium deficiency can cause a lack of appetite, weight loss, and an unthrifty appearance. The maximum required amount of potassium is 1% of feed intake with the remainder being excreted in the urine if water intake is not restricted.
Sulphur is a macromineral but requirements in the diet have not been determined. Sulphur is important for the growth of hooves and hair, reducing the growth of scar tissue, cartilage, collagen, joint fluid, enzymes, and exercise recovery. It is generally used in the body as heparin, the sulphur containing amino acids, chondroitin sulfate, insulin, and the B vitamins thiamin and biotin. Heparin is an anticoagulant, Amino acids are involved with the structural components of bodily proteins and enzymes, chondroitin sulfate is involved in joint health, insulin regulates the metabolism of carbohydrates, thiamin is also involved with the metabolism of carbohydrates, and the co-enzyme biotin helps intermediary metabolism. Horses receive their sulphur requirements through the organic sulphur present in the amino acids of plant proteins. Sulphur deficiency in horses has not been observed. Excess sulphur can cause lethargy, colic, a yellow frothy nasal discharge, jaundiced mucus membranes, and laboured breathing leading to convulsions and death. Copper absorption can be affected by excess sulphur causing the appearance of a copper deficiency.
Copper is a micromineral and is generally expressed as parts per million or mg/kg as part of the diet. Copper is an important part of bone and cartilage development, as well as tendons, blood vessels, skin pigmentation, fertility, and anemia prevention. Copper deficiency can cause problems with various Developmental Orthopedic Diseases (DOD), contracted tendons, reduced mare fertility, anemia, loss of skin and hair pigment, and rupture of the uterine artery in older mares while giving birth. Copper interacts with many other minerals therefore absorption can be affected in many ways. Copper needs to be balanced with zinc to ensure optimal absorption, the ideal ratio appears to be 1:4-5 (Cu:Zn). If the ratio is less than 1:1.7 there is a risk of a copper deficiency. Often a copper deficiency can be mistaken as an iron deficiency. Sunbleaching is a classic sign of mineral deficiency, and is most likely to be caused by a lack of copper and zinc that allows the sun’s ultraviolet rays to oxidize the coat colour pigments.
Zinc is a micromineral and is generally expressed as parts per million or mg/kg as part of the diet. Zinc is an important part of over 100 enzymes, plus the formation of bone and cartilage, and also for connective tissue and skin integrity. The highest amounts of zinc are found in the eye, in both the iris and the inner lining of the eyeball known as the choroid. Zinc is considered low if it is below 40mg/kg and toxic if it is above 500mg/kg. Zinc deficiency causes skin flaking, acne like skin patches, bald spots (alopecia), poor coat quality, lack of appetite, slower growth rates, poor hoof quality, and in extreme cases it can cause skin lesions on the legs (parakeratosis). Zinc excesses are likely to occur in industrial smelter areas; symptoms include enlarged joints and growth plates, chronic swelling, and leg stiffness. Excess zinc can also cause the appearance of a copper deficiency, so the proper ratios need to be maintained at around 1:4 (Cu:Zn).
Iodine is a micromineral and is generally expressed as parts per million or mg/kg as part of the diet. Iodine is part of the components in thyroid hormones that regulate the base metabolism. Both an excess and a deficiency of iodine can cause an enlarged thyroid (goiter). Selenium deficiency can create issues with the absorption of iodine. Feeding an iodized salt block is generally sufficient to provide correct amounts of iodine to all horses except the late term broodmare. Pregnant mares fed a seaweed/kelp vitamin supplement are at increased risk of producing a foal with goiter, stillborn, weak, hairless, deformed, and parrot mouthed.
Cobalt is a micromineral and is generally expressed as parts per million or mg/kg as part of the diet. Cobalt (cobalt chloride) is considered a banned performance-enhancing supplement in the racing industry. Horse forages contain naturally occurring cobalt that is considered to be at adequate levels for horses. Cobalt has no known function inside the horse except as a component of vitamin B12. The recommended minimum amount has been set at 0.05 mg/kg of feed. It has also been determined that too much cobalt can be toxic. Various studies have determined that excess cobalt can cause symptoms ranging from colic like symptoms, to excessive sweating, anxiety, trembling, and collapse. Cobalt should not be supplemented in a horse’s diet.
Chromium is involved in lipid and carbohydrate metabolism as well as aiding glucose clearance. It has been determined that chromium supplementation has been beneficial to healthy horses by enhancing glucose regulation. In insulin resistant horses, some have shown some benefit but in others there has been no change to insulin regulation, this is likely due to no chromium deficiency present. Chromium is found in plants in neutral and acidic soils at required levels, therefore a horse is unlikely to need supplementation unless their forage is grown in alkaline soils. In general, supplementation of chromium in a horse’s diet is not required.
Iron is a micromineral and is generally expressed as parts per million or mg/kg as part of the diet. Iron is key in the production of hemoglobin, myoglobin, cytochromes, and many enzyme systems. It is also important for oxygen transport and cellular respiration. It is generally found in required amounts in horse’s feed. Often complete feeds will over supplement the amount of iron required, with extreme amounts leading to death. Anemia caused by an iron deficiency in the horse is extremely rare and is usually caused by a copper deficiency instead. Supplementation of iron can prevent the proper absorption of calcium and therefore will likely cause bone issues in the horse. Excess iron also affects the proper absorption of copper and zinc. Excess iron in the liver can cause liver necrosis (damage) and liver failure.
Manganese is a micromineral and is generally expressed as parts per million or mg/kg as part of the diet. It is required for carbohydrate and lipid metabolism, and also for growth, fertility, and the formation of cartilage and bone. Deficiencies of manganese may contribute to limb abnormalities and curved legs/ windswept legs in newborn foals, however no studies have been conducted to verify this. Decreased growth rates in yearlings have been reported with reduced manganese daily intakes. Forages contain 40-140mg/kg and concentrates (except corn) contain 15-45 mg/kg of manganese, therefor supplementation should not be required unless the diet consists of a high amount of corn.
Silicon is important for bone development, cartilage health, and the prevention and treatment of degenerative joint diseases. Silicon is generally found in a form that cannot be absorbed by the body. If a lactating mare is fed absorbable silicon then there will be more available for the foal. Silicon is found in forage and grains, and is not generally supplemented at this time.
Nitrate poisoning in the horse is rare. Cattle pastured with horses will show symptoms before the horse as they have tolerance levels of 0.44% of dry matter intake. No safe levels of nitrates for the horse have been determined, but it is felt that the horse may be able to tolerate levels as high as 2% of dry matter intake. The most common methods of poisoning include direct ingestion of fertilizer, eating forages grown on areas of spilled fertilizer, and drinking contaminated water. Symptoms of nitrate poisoning can include colic, diarrhea, elevated heart rate, muscle tremors, abnormal gait, shaking, seizures, weakness, respiratory difficulty, a blue to brown discoloration of the gums, and death. Nitrates damage the bloods ability to carry oxygen so if blood is drawn it may appear a chocolate brown colour instead of a deep red.
A feed additive is a substance that does not provide essential nutrients directly, but might affect the horses feed consumption, performance, and health, or the characteristics of the feed. Health Canada states that “substances that are used in food to maintain its nutritive quality, enhance its keeping quality, make it attractive to or aid in its processing, packaging or storage are all considered to be food additives.” (www.canada.ca/en/health-canada/services/food-nutrition/food-safety/food-additives)
Additives in the manufacturing process:
Additives that are added to feed and are non-nutritive are known as technical additives. Antioxidant preservative compounds are added to feeds to stabilize fats and vitamins. When fats break down the feed deteriorates and loses quality by discolouring, turning rancid, becoming less palatable, or losing potency. Colour additives are included to enhance or accentuate natural feed colours as a marketing and consumer appeal tool. Flavor additives will be used to mask off-odor and off-taste components of a feed. Horses tolerate many different flavors but seem to show a preference for banana and fenugreek, and an aversion to nutmeg, coriander, and echinacea. Pellet binders are generally some form of clay and are used to create a cohesive pelleted feed and to reduce crumbling of the pellet prior to feeding. Anticaking agents are used in powdered or crystalline feeds to prevent lumping, clumping, or caking. Mineral oil, paraffin, petrolatum, or petroleum jelly is used in mineral mixes to reduce dust. Fat emulsifying agents, gum stabilizers, and various sequestrants are also used in the manufacture of horse feeds.
Additives affecting horse performance and health:
Medicinal compounds such as antibiotics and anthelmintics (antiparasitics/dewormers) added to feeds require extensive study, safety documentation, and determination of effectiveness before being allowed for use as an approved drug. Other items that are added to feeds to improve health, disease prevention, and performance are increased essential nutrients above recommended amounts, food components that are known to have a vital role in metabolism but are not recognized as an essential nutrient for horses, and substances that have no know metabolic function yet there is thought that the substance augments body health or performance. There is concern surrounding the effectiveness and safety of some of these ingredients. The horse should be fed a complete and balanced diet before any additional special supplementation is considered.
A normal healthy horse will receive adequate antioxidants in its diet, with studies finding no added benefits with additional supplementation.
Direct fed microbials are commonly referred to as probiotics. Probiotics are live lactic acid bacteria found in the intestinal interior of heathy animals. There has only been a few studies about the effectiveness of probiotic supplementation; current results show little to no improvement to horse health, and there are concerns around the safety and quality control of the products. Probiotics have a potential use after a course of antibiotics to temporarily repopulate the hindgut microbes until the natural population is re-established as many gut bacteria can be destroyed by antibiotics. Individual horses each have a unique microbial population based on the type of feed they ingest that also varies throughout the time of year, causing great difficulties in balancing probiotics in a beneficial manner.
Various enzymes have been added to feed in an attempt to improve the digestibility. Studies have shown either a slight decrease or a low to moderate increase in digestibility of feeds when supplemental enzymes are added.
Oligosaccharides or prebiotics are complex poly-saccharides (sugars) that have the potential of beneficial effects on horse health by increasing the stability of intestinal microbial populations. Horses that would benefit from prebiotics are horses undergoing feed changes, transportation stress, and other environmental changes that can affect intestinal health.
Many herbs and botanicals that are recognized as safe are used as flavoring or seasoning agents in foods. Herbs in their whole form will have some nutritive value such as fibre, vitamins, and minerals but generally are not fed in large enough amounts to add to the dietary nutrient content. Any claim that the “dietary use of herbs or botanicals with the intention of preventing or treating a disease or altering body structure, function, or performance defines the supplement as a drug, thus requiring regulatory evaluation. Data supporting such efficacy of use and safety in the horse are not available” (NRC, 2007). This being said, there are many herbs and botanicals that have medicinal properties, but being unregulated there may be adverse reactions in the horse, or adverse interactions with other herbs or drugs that are not recorded or monitored so care must be taken with their use.
Joint supplements containing glucosamine, chondroitin sulfate, and possibly manganese ascorbate, are some of the most common feed additives given to horses. As these supplements have the potential to delay, stabilize, or possibly repair osteoarthritis or reduce joint degeneration, they fit into the definition of a drug so require effectiveness and safety documentation. Unfortunately, it has been found that there can be a significant discrepancy between actual composition and label claims by many manufacturers.
Methylsulfonylmethane (MSM) is a form of organic sulphur that can be digested by the horse. It is an effective anti-inflammatory and pain reliever as well as providing benefits to joint health, hooves, and hair.
The essential fatty acids omega-3 (alpha-linoleic acid) and omega-6 (linoleic acid) have beneficial anti-inflammatory properties. Supplementation of omega-3 could have a possible positive result for horses suffering from allergic type reactions like heaves or fly-bite hypersensitivity. Canola oil or Flaxseed is the best source of omega-3 and omega-6 for horses.
Medicinal Compounds in feeds are generally antimicrobial agents referred to as antibacterial (antibiotic) compounds. At this time no antibiotics and only the two anthelmintics (dewormer) febendazole and pyrantel tartrate are approved for inclusion in horse feed. There is concern about feed cross-contamination during processing, of non-approved antibiotics used in other animal feeds. The concern is based on horse sensitivity to some antibiotics and reduced intestinal microbial populations.
Yeast cultures, dried yeast, and yeast extracts may be added to feeds to potentially increase gut fermentation, and improve digestibility of fiber and other nutrients. Constant rather than occasional supplementation may have benefits when high grain or concentrate diets are fed.
Many people like to give their horses treats. Traditionally treats were sugar cubes, apples and carrots. While these are still popular, people can also give their horses a variety of almost any fruits and most vegetables as well as peppermints and bread. Most treats are quite high in sugar so care must be taken on the amounts given. Treats can interfere with hindgut microbial populations just like any other change in feeds, so should only be given in small amounts occasionally.
Horse favorites include: Apple, Blueberry, Cherry (no pits), Grapes (red ones have Resveratrol which is used as a supplement), Banana and peel, Watermelon and rind, Sugar cubes, and Peppermints.
Horses also like: Blackberry, Raspberry, Strawberry, Orange and peel, Grapefruit, Lemon, Lime, Papaya (no seeds, no peel), Mango (no pit, no peel), Raisin, Snow Pea, Cantaloupe and other melons, Apricot (no pit), Nectarine (no pit), Peach (no pit, no peel), Pear, Plum (no pit), Pineapple, Date (no pit), Fig, Carrot, Turnip, Rutabaga/Swede, Beetroot and greens, Cucumber, Parsnip, Roasted Peanut and shell, Sunflower seeds, Pumpkin, Coconut, Green Beans, Lettuce, and Celery.
Don’t feed horses: Avocado, Broccoli, Cauliflower, Spinach, Raw garlic, Onion, Tomato, Peppers, Potato, Cabbage, Brussels Sprout, Rhubarb, Milk, Cheese, Yogurt, or Ice Cream.
You can feed a small amount of chocolate, but some horses can colic or suffer seizures and horses that attend events where drug testing occurs may test positive for banned substances due to the caffeine. Bread products may be fed in small amounts but might become a doughy mass that can cause choke.
Nutrient Requirements for Various Stages of Life
Hair and blood samples are not reliable to determine if the horse has adequate amounts of nutrients in its diet due to the homeostasis process of blood. The most effective way to determine which nutrients are deficient or in excess in a horse’s diet is to start with a pasture or hay test, and then take into account any other feeds. You can then decide on the formulation of a custom feed program and mineral mix based on the whole diet intake. Without a pasture and/or hay nutrient test, you won't know which nutrients are excessive or deficient and you won’t know whether critical mineral ratios are balanced to ensure proper absorption. It is possible to utilize standard data tables to determine average amounts of nutrients in different forages. These forage tables can be found at www.feedpedia.org.
Nutrient Requirements for the Mature Horse
Many horses are able to be maintained at an acceptable body weight by a forage or hay only diet while at a maintenance level of work. If more energy is required to maintain weight due to work level requirements then traditional grains or modern concentrates can be added to the diet. The mature horse should be fed 2-2.5% of its body weight in feed per day depending on the amount of work being performed. The ration should also contain 9-10% protein. The feeding of biotin (B7), zinc, and copper above recommended requirements has been shown to increase hoof wall strength and improve hair coat quality.
An underweight horse can effectively gain weight by as little as a 10-15% increase in feed quantity. A 500kg/1,100lb horse eating 2% of its body weight daily (10kg/22lbs) will effectively gain weight at a safe rate, by the addition of 1.0-1.5kg/2.2-3.3lbs of feed. A severely injured horse will benefit from increased protein in its diet to aid in the healing process. A horse fed large amounts of poor quality, indigestible or hard to digest fiber will have more forage in its cecum and large intestine so will develop a visibly distended “hay belly”. The appearance of “hay bellies” can be reduced by feeding higher quality forages and grains.
In cold weather increasing the amount of roughage fed to the horse is more effective for maintaining warmth than feeding grains or concentrates. For horses acclimated to northern areas, forage should be increased at around -15C/5F. For horses acclimated to southern areas, forage should be increased at around 5C/41F. In warm weather over 25C/77F the horse will require additional water and salt. Work levels for the mature horse must also be taken into consideration when designing a feed program.
Maintenance, feed 2% of bodyweight – basic level to maintain weight, no work
Light work, feed 2% of bodyweight – pleasure riding, local shows
Medium work, feed 2.25% of bodyweight – Ranch work, roping, cutting, barrel racing, jumping
Heavy work, feed 2.5% of bodyweight – race training, endurance riding, polo, late pregnancy
Very heavy work, feed 3%+ of bodyweight - lactation
Nutrient Requirements for the Breeding Stallion
In general a stallion requires slightly more feed than a gelding or non-breeding mare. Going into the breeding season he should be at a body condition score of 5-6. If he loses weight due to nervous activity such as pacing or a poor attention span causing a reduced amount to be eaten, then supplementation with added fats can help without increasing the amount fed. The addition of omega-3 to the diet 90 days before the breeding season can help improve fertility levels. During the breeding season he will require up to 20% more feed if he is in heavy use (70+ covers/month).
Nutrient Requirements for the Pregnant Mare
The common rule is that a broodmare that in not lactating only requires her standard ration until the last three months of pregnancy. This is only true if she is on a balanced feeding program that covers all nutritional requirements, she has no mineral imbalances, and is at a body score of 5-6. Most feed programs will have the correct amount of energy (calories) and protein but may not have minimum required amounts of the essential trace minerals, especially if she is on a straight pasture or hay diet. A developing fetus cannot grow to its full potential and may be born weak, have bone and cartilage developmental issues, or potentially be stillborn if the mare is lacking in important minerals or protein. Many of these fetal developmental issues cannot be rectified after birth so the foal could have problems throughout its life. A mare, just like a woman needs to have her nutrient deficiencies addressed right at the start of her pregnancy or better yet prior to conception.
Prior to conception and throughout the pregnancy additional omega-3 and omega-6 should be supplemented. Canola or Flaxseed oil provide the best omega-3 and omega-6 ratios. The increase of these fatty acids have shown positive results in early pregnancy for the retention of the embryo and in later pregnancy for the creation of high quality colostrum. Studies have found that pregnant mares that are deficient in protein also have low progesterone levels (NRC 2007). Progesterone is critical to the maintenance of early pregnancy. The pregnant mare should receive at least 60% of her protein requirements as high quality proteins.
In the last 3 months of a mare’s pregnancy the fetal bones will be beginning the process of mineralization, therefore it is of great importance to ensure that the mare is receiving an increased amount of protein in her diet in the range of a 14%-16% protein mix. The pregnant mare will also need increased amounts of dietary energy (calories) starting at 8 months. At 8 months her energy requirements will increase 11-19% above maintenance requirements. At 9 months energy requirements increase to 13-21% above maintenance levels. Finely, at 10 months her energy requirements will increase to 20-28% above maintenance levels. A pregnant mare could end up consuming as much as 3% of her body weight per day. Scientists have speculated that a pregnant mare can adjust for marginal energy, protein, and mineral deficiencies by utilizing her bodily reserves and prolonging the gestation time (Meyer 1996).
Mares fed increased amounts of organic selenium in the form of selenium yeast rather than inorganic sources and a corresponding increase in vitamin E, will have less incidences of retained placentas, as well as increased selenium levels in her colostrum and milk and in the newborn foal. It is recommended that mares in their last month of pregnancy be fed 3mg of selenium and 1,600IU of vitamin E per day. Fescue and perennial ryegrass pasture or hay should not be fed to pregnant mares due to the risk of major pregnancy complications unless it is guaranteed endophyte-free.
Nutrient Requirements for the Lactating Mare
The lactating mare will require a larger ration of water than any other horse. She will drink 50-80% more water to produce enough milk for her foal. If she does not receive enough water her milk production will be reduced and will not return to a previous level when adequate water is provided. A mare will produce at least 3kg/6.6lbs of milk per 100kg/220lbs of body weight in early lactation and 2kg/4.4lbs of milk per 100kg/220lbs of body weight in late lactation, resulting in 1.9% - 3.9% of her body weight in milk per day.
The mare will use her own stored reserves to produce enough milk for her foal so to maintain her weight she should be fed as if she is in very heavy work. She will likely need 2.5% of her body weight per day in feed but could require as much as 3-3.5% of her body weight. While it is possible to maintain a horse solely with pasture it is unlikely that a lactating mare will be able to consume enough to maintain body weight due to the high moisture content of fresh pasture grasses and may need additional feed supplementation. She should also be consuming 16% protein, as much of this will go to the foal to aid in its rapid early growth. Care needs to be taken to ensure that the requirements for protein (lysine), calcium, phosphorus, copper, and zinc are being met. The lactating mare should receive at least 60% of her protein requirements as high quality proteins. A mare consuming a high forage ration will produce milk that has a higher fat concentration than a mare fed a high concentrate ration, therefore the foal will have a better rate of growth. If a mare is low in critical nutrients it may not be noticed until there are significant problems with the foal, such as poor condition and developmental orthopedic diseases.
Nutrient Requirements for the Foal aged 0-3 Months
At birth the foal’s first nutrition is colostrum, which must be consumed in adequate amounts within the first 24 hours and preferably before the foal is 8-12 hours old, to ensure passive transfer of disease immunity. Ideally a foal will receive 1500ml/6 cups of colostrum per 45kg/100lbs of body weight in its first 6 hours. A study (Hoffman et al, 1999) found that when a mare’s vitamin E was doubled from the recommended 2IU/kg of bodyweight to 4IU/kg of bodyweight, the newborn foals had better serum immunoglobulin G (IgG) titers than the control foals. This study suggests that when a pregnant mare reaches the 10th month of pregnancy an increase in her vitamin E can be beneficial for the newborn foal. Increasing the mare’s selenium intake through the use of organic selenium yeast improved the foal’s selenium status at birth as well.
At birth the newborn foal will weigh approximately 9.7% of the mare’s weight, and will triple that weight in the first 4 months. A mare’s milk will contain around 22% protein, 16% fat, and 58% carbohydrates/sugars. A foal will begin to eat feces at 5-10 days old to start to populate its intestines with the required microbes to digest forages, this is likely to cause diarrhea that is often termed “foal heat diarrhea” due to the timing with the dams first breeding cycle after foaling. Young foals can then be fed a supplemental milk based feed or a balanced foal pellet as soon as they show interest in trying to eat their dam’s food. Prior to 2 months of age a foal has very little ability to digest forages and concentrates and will have all its nutritional needs met through the dam’s milk but will be actively sampling all the dam’s feed. By 2 months of age the foal will be consuming the maximum amount of milk. As the foal begins to consume more forages, the milk quantity and quality will begin to decrease.
It is extremely important to ensure that the calcium to phosphorous ratios for growing horses are maintained balanced at 1:1 to 2:1. High calcium alfalfa hays can contribute to a number of developmental orthopedic diseases. A growing horse requires 14%-16% protein throughout its total growing period. All growing horses should receive at least 60% of their protein requirements as high quality proteins. If the foal shares feed with the dam, the feed needs to be balanced for the foal and not the dam. If a foal is allowed to eat a ration not designed for its specific needs, it may consume enough to gain weight but will likely receive an inadequate nutrient supply to enable proper growth and skeletal development, this can result in a fat foal that has an improperly developed musculoskeletal system, risking developmental orthopedic diseases. Foals are more tolerant of heat than they are of cold, and are able to tolerate temperatures as high as 38C/100F before requiring additional water or salt.
Nutrient Requirements for the Orphan foal
It is possible for an orphaned foal to grow and mature to its full genetic potential the same as those raised on a mare. A newborn foal requires its mother’s colostrum within the first 24 hours after birth, and preferably before it is 12 hours old. If supplemental colostrum is not provided then a plasma transfusion is needed. The orphan foal will do best with a nurse mare but goat’s milk or commercial horse milk replacer will work. When starting a newly orphaned foal on milk replacer start with 5-10% of body weight divided into 24 feedings to mimic natural feeding processes, gradually increasing amount over a 10 day period. Feed the foal according to the manufactures directions and in the amount of 10-15% of body weight per day for larger foals. When bottle feeding, a lambs nipple works best, but the foal should be transitioned to a bucket as soon as possible. At one month the foal can be offered a high protein creep feed and quality hay, the same as a normal foal. The foal can be weaned off milk replacer at 3 months of age if a milk based creep feed is provided until it is 4 months of age. Ensure that fresh water is available at all times.
Nutrient Requirements for the Foal Aged 3-6 Months
As the foal gets older the digestive enzymes change so that by the time it is 3-4 months old it can digest more forages and concentrates. By 4-5 months of age a foal has a lowered ability to digest milk products and will obtain almost all of its dietary requirements through forages and concentrates. Nursing episodes are reduced to about 1.5 times per hour by 5 months of age. Continued vigilance is required to ensure that the foal is given the correct amounts and proportions of nutrients through this growth phase.
In North America it is considered standard to wean foals at 4-6 months of age, while in Europe it is more common to wean at 6-12 months of age. It is felt that most feral foals are self-weaned by 8 months of age which coincides with the worst part of the winter when the Dam has the lowest amount of available forage for herself. Care must be taken when weaning a foal, to ensure that it is being fed adequate amounts of hard feed so when the milk portion of the diet is removed, significant weight loss does not occur. This means that a foal should be eating close to the amount of solid food it will need without its dams milk before it is weaned. Care also needs to be taken to ensure that there is not a sudden increase in the amount of hard feed given as there is a significantly increased risk of Developmental Orthotic Diseases (DOD) if this happens.
A growing horse requires 14%-16% protein throughout its total growing period. Lysine is the most important growth-limiting amino acid and should be monitored to ensure that the protein source has adequate amounts. Foals younger than 8 months have better growth rates using a milk based protein source rather than other grain sources. A protein deficiency even with adequate amounts of energy/calories fed, will result in loss of weight, poor growth, and poor hoof development. All growing horses should receive at least 60% of their protein requirements as high quality proteins. Calcium balance is important for skeletal development to ensure the horse’s full usefulness as an adult. The weaned foal should be consuming between 2-3.5% of its body weight in feed per day. The weanling cannot digest roughages as easily as an older horse, so should be fed a higher proportion of concentrate to roughage to help avoid a potbellied, scruffy appearance.
Nutrient Requirements for the Weanling Aged 6-12 Months
Many young horses are fed to maximize their growth to give the appearance of a larger than average foal for its age, aiding the breeder in selling it. This occurs quite often with racing Thoroughbreds, Standardbreds, Warmbloods, and Quarter Horses. Maximal growth can be undesirable if adequate nutrients are not provided to ensure that the bones develop at the same rate. Maximal growth rates will not increase a horse’s final height, as that is predetermined by genetic factors. Periods of growth that fluctuate between slow growth and maximal growth can also cause developmental problems. Optimal growth is better as the young horse will develop at a steady rate and have a reduced risk of developing any of the Developmental Orthotic Diseases (DOD). Maximal growth generally causes a horse to reach its full height at 2 years of age while optimal growth allows a horse to reach full height at 4-5+ years. If a growing horse is fed to maintain a body score of 5-6 then they will reach their full genetically determined size.
A growing horse requires 14%-16% protein throughout its total growing period, this equates to 2.1 g/Mcal DE lysine and 50 g/Mcal DE crude protein in a weanling expected to reach 500kg/1,100lbs. All growing horses should receive at least 60% of their protein requirements as high quality proteins. A growing horse also requires feed rates at approximately 2.5-3.5 % of its body weight to maintain optimal growth rates. Young growing horses are less tolerant of the cold than mature horse so should be fed increased amounts of forages in northern climates when the temperature reaches a range of -11C/12F to 0C/32F depending on the horse. In warmer climates the growing horse will likely need increased forage at approximately 10C/50F.
Nutrient Requirements for the 1-3+ year old
A growing horse requires 12%-16% protein throughout its total growing period. Slower growing horses may need to be fed elevated protein levels up to the 4th or 5th year. The young growing horse should also be fed 2-2.5% of its body weight per day in total feed, and will likely require more depending on its level of work once it begins training. Once a horse reaches one year of age their digestion is mature enough to digest roughages like an adult horse, so can receive most of their requirements from forages with a smaller amount of concentrate to balance growth. The 12-18 month old horse will likely be consuming the same amount of forages as a mature horse at maintenance. A young horse that does not shed out properly in the spring and has a rough thick hair coat is not receiving enough protein in its diet. All growing horses should receive at least 60% of their protein requirements as high quality proteins. The growing horse should be monitored closely to ensure a body condition score of 5-6 is maintained.
Nutrient Requirements for the Senior Horse
A horse becomes classed as an aged/senior horse somewhere in their late teens or early twenties depending on the individual horse. A senior horse that has difficulty chewing can be fed easier to chew foods in the form of soaked beet pulp, soaked hay cubes, haylage, chopped hay, and complete feeds. For an extruded feed to be classed as a complete feed it must contain at least 14% crude fiber or higher. Easily chewed feeds are important to maintain feed digestibility ensuring that the senior horse receives all the nutrients possible. Older horses may also have a reduced ability to digest fiber, protein, and phosphorous. Supplementing the amino acid lysine at 0.25% of dry matter per day and the amino acid threonine at 0.2% of dry matter per day could help maintain muscle mass. The older overweight horse is susceptible to Cushings, Insulin Resistance, Thyroid Tumors, and Metabolic Syndrome. The older horse can also have liver and kidney problems that can result in weight loss and loss of appetite.
Nutrient requirements for Donkeys, Burros, Asses (Equus Asinus) and Mules
The donkey is physically and behaviorally different than the horse. It evolved in a hot semi-arid environment that adapted it for a different feeding strategy than the horse. A mule has attributes of both the donkey and the horse. When grazing a donkey or mule will select high quality forages but is quite capable of consuming more mature, less digestible, woodier plant material than a horse. They require less feed than a horse and should be fed 1.75-2.25% of body weight. Donkeys generally consume 64-69% of what the same size pony will. A donkey can survive with less frequent water consumption than a horse. They tolerate the effects of dehydration better and have the ability to fully rehydrate within minutes of drinking. The donkey is better able to digest forages due to more efficient hind gut digestion and a slower rate of passage. A donkeys resting metabolism is 20% lower than a horses. Energy requirements (calories) should be calculated at 75% of a horse. Crude protein requirement range between 3.8% and 7.4% of the diet. Feed requirements can be met by forage alone, as obesity is a major concern for donkeys in non-arid regions of the world.
Designing a Feed Program
Implementing a revised or new feed program for you horse can be quite the tricky endeavor. Each horse requires a different amount of feed to maintain optimum weight and health depending on breed, stage of development, amount of work, environmental factors, and quality of forage available. As previously discussed the average horse requires 2-2.5% of its body weight in total dry food per day depending on the amount of work it is performing. This can be adjusted lower for “easy keepers” but should never fall below 1% of total body weight. For horses that require more calories to maintain body weight it is possible to feed up to 3% of body weight. There are special cases that do not follow the general practices such as starved horses, horses with nutritionally related diseases and racehorses under training. A horse on free choice pasture or hay can easily eat 3%-3.5% of its body weight in a day so may tend to be overweight.
Horses in the wild will graze for 14-16 hours a day, and travel up to 16 km in the search for enough nutrients. A horse on pasture will usually consume enough forage in 12 hours for its nutritional requirements and travel far less. Typically a feed program should be devised by determining required forage, then amount of grain or extruded feed required to maintain desired weight or rate of growth, then amount of ration balancer or mineral supplement required to ensure all nutrient levels are met. The amount fed will then have to be adjusted based off of the horses overall condition; the horse should be at a body score of 5-6 with a flat back when viewed from the back, the ribs should not be seen but will be easily felt, the belly and flank should be gently rounded, and the coat should be shiny and soft. When changing the amount or type of feed in your horse’s diet it is important to make changes over the course of several weeks to allow the microbes in the hind gut to adapt. The quality of the ingredients in your feed program are also important as the horse will be able to digest them more efficiently and then you will actually be able to feed less. It will take at least 45 days to see a change in a horse’s condition once the horse is completely on the new feed program.
Forages in the form of hay or pasture are the major portion of a horse’s daily nutrient requirement. Forages contain mostly structural carbohydrates.
Grain/ Extruded feeds/ Concentrates
Regardless of what type of non-structural carbohydrate you feed, it has been determined that the maximum amount that can be fed to a horse at any one feeding should be no more than 0.35-0.4% of body weight (Potter et al.). For a 500kg/1,100Lbs horse this would be 1.75-2kg/3.85-4.4Lbs of concentrate per feeding. If a horse requires more concentrate per day than what can be consumed in the average 2 feedings per day, then it is important to increase the number of feedings rather than increase the size of a feeding beyond suggested amounts. Race horses and endurance horses in heavy work are often fed up to 32%-36% non-structural carbohydrates in their diet. This equates to roughly 4.5kg/10lbs of grain. Therefore the average horse is likely to not need as much grain in their diet as is typically fed. Studies have also show that feeding hay two hours before or with concentrates has very little difference in digestion rates but concentrates fed alone have a significant difference in blood glucose levels, where the glucose levels spike then drop off (Pagan).
Ration balancers are an effective method of providing supplemental protein and minerals when a large amount of concentrates are not required for a horse.
Mineral supplements should be based on the forage and whatever extra concentrates are being fed. They would then supply the part of the horse’s nutrients that is not met by the base forage. Currently, supplements added to the horse’s diet should be considered a requirement rather than an exception for the modern horse owner. It can be expected that a horse will require 44ml/1.5oz – 89ml/3oz of a commercial powdered mineral supplement to receive the required amount of mineral. Trying to balance your own vitamin and mineral interactions is virtually impossible. If you attempt to supplement an individual mineral on its own you will likely create an imbalance with other minerals. Interactions between the various vitamins and minerals is an extreme balancing act as the diagram shows.
Understanding a Laboratory feed analysis
It is becoming more common for hay and grain producers to send samples of their crop to a lab for analysis. This allows informed horse owners to have a more accurate breakdown of their feed than one obtained from standardized feed composition tables. It is a good idea to compare a feed analysis against the standard tables as this will give you a better understanding of the actual quality of your feed rather than just looking at the numbers. Most of the components listed on your analysis sheet will be self-explanatory like the percentages for crude protein, and minerals. Others may not be so easy to interpret, like the breakdown of structural carbohydrates (fibre) and non-structural carbohydrates (starches and simple sugars). On an analysis form, the most common method used to list the fibre components is using the Van Soest detergent system which breaks forage down into its ability to be digested by ruminants like cattle. The following is an explanation of some of the analysis terms.
AS Fed/As Sampled vs Dry Matter The “As Sampled” column contains the nutrient percentages with the moisture content included. The “Dry Matter” column contains the nutrient percentages without the moisture content. Using the “Dry Matter” content of forages and other feeds is the recommended method to compare different plant products and to determine requirements of a feeding program.
Moisture Horse hay should have a moisture range from 10-16%. Hay that has less than 10% moisture will be brittle and shatter easily. Hay that has more than 17% moisture will have a greater tendency to mold. Hay that has a moisture content of greater than 25% is at risk for severe heat damage and has a high fire risk.
Dry Matter The dry matter percentage is important to consider, with the better hays having a dry matter percentage of 84-90%. “Animals will have to consume more of a wetter feed to receive the same amount of dry matter as they would from a drier feed. For example, if an animal consumes 20 lbs of hay at 90% dry matter, it consumes 18 lbs of dry matter (20 x .90). If haylage at 40% dry matter was to be substituted for the hay, it would have to consume 45 lbs. of haylage (18/.40) to receive the same amount of dry matter” (Dairy One, Understanding & Significance of Forage Analysis Results).
Crude Protein (CP) CP is the total protein in the sample and includes both true protein and non-protein nitrogen. Lab reports, feed tags, and feed tables normally express the protein amounts as crude protein. Depending on the life stage of a horse, crude protein requirements range from 12-18%. Forages of less than 10% crude protein could have higher levers of NSC and are not suited to be horse feed.
Soluble Protein (SP) SP is an estimate of the amount of crude protein that is able to be digested in the rumen of a cow. It has limited value for the horse.
Degradable Protein (RDP) RDP is the total protein consisting of soluble protein and proteins that have an intermediate digestibility in the rumen of a cow. It has limited value for the horse.
Acid Detergent Insoluble Protein (ADIP) or Acid Detergent Insoluble Crude Protein (ADICP) ADICP is the percentage of the total protein that is unavailable to the horse due to heat damage. ADIP may also be labeled as acid detergent insoluble nitrogen (ADIN) or acid detergent fibre protein (ADF-P).
Neutral Detergent Insoluble Crude Protein (NDICP) NDICP is the percentage of the protein that is not digested in the rumen of a cow but is digested in the intestines of non-ruminants. It has limited value for the horse.
In Vitro True Digestibility (IVTD) A laboratory process that copies the digestion of a forage by a cow. The resulting digestibility measure can be used to estimate energy.
Neutral Detergent Fiber (NDF) The percentage of plant cell wall material that includes cellulose, hemicellulose, lignin. silica, tannins and cutins. Some analyses may be presented as aNDF or aNDFom, this signifies a greater amount of steps used to determine accurate results. The higher the percentage of NDF the less forage your horse will be able to consume on a daily basis, as it directly correlates to the amount or bulk of the feed. A NDF value of less than 53% is representative of better quality forages. Horses should be fed forages that contain less than 50% NDF. A horse can consume forages higher than 50% NDF but will require more, which results in increased length of time to consume and digest the forage and the appearance of a larger “hay belly”.
Neutral Detergent Fiber Digestibility (NDFD) A laboratory process that copies the digestion of a forage by a cow. The result is the percentage of NDF that is potentially digestible and is also used in energy calculations. The NDFD can be used to rank forages for potential digestibility of fibre.
Carbohydrate Digestion Rate (Kd, %/hr) This is an expression of the rate of microbial fermentation in the cow. It has limited value for the horse.
Acid detergent Fiber (ADF) The percentage of plant cell wall material that is the most indigestible parts of the forage. When ADF is subtracted from NDF then the amount of digestible fiber in the form of hemicellulose can be determined. A forage low in both NDF and ADF is able to provide both a higher potential intake and a higher amount of digestibility compared to a forage with high percentages of NDF and ADF. An ADF value of less than 41% is representative of better quality forages, while forages higher than 45% may have limited nutritional value. Ideally horses should be fed forages with an ADF percentage lower than 31%, but can do well with levels as high as 40% if allowed more forage to compensate for the higher levels.
Lignin Also known as cell wall phenolics it is an indigestible structural fibre component of plants. It is found in the fibrous portion of a plants leaves, stems, hulls, and cobs. The more lignin in a plant the harder it is to access and digest the digestible fiber component.
Non-fiber carbohydrates (NFC) Carbohydrates that are not part of the plant cell wall and are not accounted for with the neutral detergent fiber. NFC’s are a major energy source for the horse and are generally composed of starch, sugar, pectin and fermentation acids. NFC is calculated using the following formula: 100% - (CP% + (NDF% - NDICP%) + Fat% +Ash%)
Ethanol Soluble Carbohydrates (ESC) ESC are represented by monosaccharide and disaccharide carbohydrates that are soluble in ethanol. They consist mainly of simple sugars, with very small amounts of fructans.
Water-soluble carbohydrates (WSC) WSC are represented by oligosaccharide and polysaccharide carbohydrates that are soluble in water or the gastrointestinal tract as well as the ESC portion of the carbohydrates. Water soluble carbohydrates consist mainly of various forms of starches, sugars and pectin. Fructans are also included in the water-soluble carbohydrates. The difference between ESC and WSC is a reflection of the amount of fructans in the forage and is important for the prevention of laminitis. The average horse can tolerate WSC levels of 20% or higher but should be fed forages that are generally 10-17% WSC. Horses that are sugar sensitive or metabolically challenged should be fed forages that are less than 10% WSC.
Starch The main carbohydrate that is found in grains, seeds, and the root portions of a plant. Starch is the main component of non-structural carbohydrates. The horse should be fed a forage that is less than 18% of a combination of WSC and starch. Horses that are sugar sensitive or metabolically challenged should be fed a forage that is less than 10% of a combination of WSC and starch.
Non-structural Carbohydrates (NSC) - The total amount of non-structural carbohydrate in the forage is determined by adding the water soluble carbohydrate and starch amounts together.
Fat Fat is a nutrient that is energy dense and can contain from 2.25X to 2.8X the amount of energy found in carbohydrates. There are several different methods to measure fat in a feed analysis depending on your particular lab. Your report will list it as fat, crude fat ether extracted (EE), or total fatty acids (TFA).
Total Digestible Nutrients (TDN) TDN is the total digestible amount of neutral detergent fiber (NDF), protein, non-structural carbohydrates (NSC), and 2.25X the fat. One kilogram of TDN is equivalent to 4.4 megacalories (Mcal) of DE.
Horses Total Digestible Nutrients (TDN) Horse TDN is slightly different than TDN if it is on your feed report. It is the total digestible protein, crude fiber, nitrogen-free extract (NFE), and 2.25X the digestible fat. Horse TDN is estimated from the digestible energy (DE) percentage.
Digestible Energy (DE) There are several ways that the amount of energy in a feed can be accounted for. Most will not be shown on a forage analysis, with the exception of digestible energy. DE is the total energy (Mcal) available to the horse after the energy lost in the feces is accounted for. DE is a measure of the amount of calories a forage will provide the horse.
Net Energy for Lactation (NEL) NEL is the estimated energy in a feed for basic maintenance plus lactation, or basic maintenance in the last two months gestation for dry cows. It is not used for horses.
Net Energy for Maintenance (NEM) NEM is the estimated energy in a feed for basic maintenance where the horse neither gains nor loses weight.
Net Energy for Gain (NEG) – NEG is the estimated energy in a feed that can be used for body weight gain above the amount required for maintenance.
Ash Ash is the term used to express a measure of the total mineral content of the feed. It is called ash because the feed sample is weighed and then incinerated. All of the organic material (protein, fiber, fat, etc.) is burnt off leaving behind just the minerals, which are then reweighed. If the ash content is greater than 12% this generally is a result of high levels of soil contamination in the forage.
Relative Feed Value (RFV) RFV is an indexed scale that ranks forages based on consumption potential and digestibility. It is determined from the percentages of ADF and NDF. RFV allows you to compare the ability of different forages to be an effective feed for your horse. The scale has been developed to depict an average alfalfa hay as having a NDF value of 53% and an ADF value of 41%. The standardized average forage has been given a representative value of 100 on this scale. Higher quality forages will have values greater than 100, and lower quality forages will have values lower than 100.
Relative Forage Quality (RFQ) RFQ is an indexed scale that ranks forages using a more comprehensive analysis than RFV. RFQ is calculated from CP, ADF, NDF, NDF digestibility, fat, and ash. It should be a more complete reflection of the forage feed value and how the forage will perform when fed. RFQ uses the same scoring method as RFV with an average score of 100, therefore the higher the RFQ number, the better the forage quality. The RFQ index is a better reflection of quality forage and should be used for determining requirements for the horse. The horse at maintenance can be fed hay that has a RFQ range of 100-115. The pregnant mare and most working horses should be fed hay with a RFQ range of 110-125. Lactating mares, growing horses, and horses undergoing heavy exercise should be fed hay that has a RFQ range of 120-135.
Milk lbs./ton This is an estimate of a dairy cows potential milk yield per ton of forage. It is not utilized for horses.
Feed Calculation Example #1:
750kg/1653lb mature horse at maintenance.
750 * 0.02 = 15kg/33lbs of feed based on 2% of body weight
The weight of the forage must be converted to the Dry Matter weight to calculate nutritional content:
Timothy hay: 6.5kg * 0.851 =5.5315kg DM
Oat hay: 6.5kg * 0.85 = 5.525kg DM
Beet pulp: 2kg * 0.91738 = 1.83476kg DM
Based on the following analysis, the neutral detergent fiber (NDF) of both forages is on the higher recommended level for the horse, even though the timothy hay is below its personal average value. This reflects hays with a high stem to leaf ratio; they are still acceptable but will take a slightly longer time to digest. The water soluble carbohydrates (WSC), non-structural carbohydrates (NSC) and non-fibre carbohydrates (NFC) in the timothy hay are double the average amount and therefor reflect a higher quality hay with more available nutrient value, and is a direct reflection of the lower NDF. This hay would not be suitable for a horse with sugar sensitivities even though the starch levels are well below the 35% limit to be considered a high starch diet. The oat hay has a low NSC number compared to its average value, this is a result of the plants being cut at an earlier stage of head development than is typical.
Even though it is available, the horse does not need a complete mineral supplement as it is only deficient in Selenium (Se), Copper, (Cu) and Zinc (Zn) as provided by the forage in the diet. While it appears to be deficient in Iodine (I), the horse should be provided with an iodized salt block that is fed free choice and will provide for any Iodine required. The horse may be deficient in Vitamins A, E, and D depending on the length of time since it had access to fresh forage or sunshine. Ideally the horse should be fed a copper-zinc and a selenium-vitamin E supplement to balance the small mineral requirement as the majority of minerals are more than adequate.
|Component||Timothy Hay||Oat Hay||Beet Pulp||Mineral||Required Amt||+/-|
|DM %||85.1 (84.4)||85.0 (85.0)||(91.738)||-||84-90||ok|
|Lignin %||5.3 (5.615)||4.0 (4.72)||(4.143)||-||<7?||ok|
|ADF %||25.3 (38.748)||34.2 (37.253)||(26.213)||-||<31-40||ok|
|NDF %||52.5 (62.350)||55.0 (58.826)||(41.156)||-||<50-53||ok|
|WSC %||22.2 (11.432)||12.3 (10.027)||(10.897)||-||10-17||ok|
|ESC %||12.0 (7.068)||10.0 (10.923)||(8.902)||-||-||-|
|Starch %||0.2 (1.649)||1.3 (0.987)||(0.992)||-||<35?||ok|
|NFC %||30.5 (19.538)||23.1 (25.187)||(44.908)||-||-||-|
|Fat %||2.3 (2.556)||2.6 (2.265)||(1.273)||-||<6, max 10||ok|
|Ash %||5.07 (7.832)||6.05 (7.136)||(7.334)||-||<12||ok|
|RFV||123 (89.368)||105 (96.429)||-||-||+100||ok|
|RFQ||152 (125.61)||137 (113.146)||-||-||110-115||Great|
|DE, Mcal/kg||2.47 (2.04)||2.29 (2.13)||1.165(2.63)||-||24.98(29.63)||+4.65Mcal|
|CP||12.0 (10.897)||15.7 (8.291)||(9.286)||-||945g (1741)||+796g|
|Ca||0.57 (0.489)||0.36 (0.301)||(1.017)||12.0||30g (63)||+ 33g|
|P||0.2 (0.239)||0.26 (0.203)||(0.089)||8.0||21g (28)||+7g|
|Calcium : Phosphorous Ratio 1-2||1.8:1||ok|
|Mg||0.15 (0.208)||0.23 (0.142)||(0.241)||1.6||11.25g (25.4)||+14.15g|
|K||1.94 (1.846)||1.75 (1.663)||(0.705)||-||37.5g (216.9)||+179.4g|
|Cl||0.71 (0.599)||1.33 (0.922)||(0.165)||-||60g (124.6)||+ 64.6g|
|S||0.21 (0.177)||0.23 (0.132)||(0.304)||0.50||22.5g (29.9)||+ 7.4g|
|Co (mg/kg)||(0.578)||(0.722)||(0.833)||30||0.8mg (8.7)||+ 7.9mg|
|Cu (mg/kg)||(8.575)||(7.545)||(8.908)||700||150mg (105.46)||-44.54|
|Zn (mg/kg)||(31.079)||(19.466)||(24.475)||4,000||600mg (324)||-336mg|
|Copper : Zinc Ratio 1:4-5||1:3.1||Low|
|I (mg/kg)||0||0||0||40||5.3mg (0)||-5.3|
|Fe (mg/kg)||(199.568)||(257.438)||(624.179)||4,000||600mg (3672)||+3072mg|
|Se (mg/kg)||(0.127)||(0.062)||(0.165)||15||1.5mg (1.35)||- 0.15mg|
Feed Calculation Example #2:
6 month old foal with an estimated mature weight of 750kg/1653lb.
Estimated weight = 324kg/715lbs.
324 * 0.025 = 8.1kg/17.86lbs of feed based on 2.5% of body weight
Actual amount fed to meet daily requirements: 11.59 kg/ 25.55 lbs of feed (3.58% of body weight)
The weight of the forage must be converted to the Dry Matter weight to calculate nutritional content:
Timothy hay: 4.5kg * 0.851 = 3.86kg DM
Oat hay: 4.5kg * 0.85 = 3.86kg DM
Beet pulp: 0.751kg * 0.91738 = 0.692kg DM
Proform Step: 1.765kg *0.9 = 1.59kg DM
Based on the following analysis, the neutral detergent fiber (NDF) of both forages is on the higher recommended level for the horse, even though the timothy hay is below its personal average value. This reflects hays with a high stem to leaf ratio. The water soluble carbohydrates (WSC), non-structural carbohydrates (NSC) and non-fibre carbohydrates (NFC) in the timothy hay are double the average amount and therefor reflect a higher quality hay with more available nutrient value, and is a direct reflection of the lower NDF. The timothy hay is deemed to be of higher quality than an average alfalfa hay and the oat hay is slightly more course than the same average alfalfa hay but is still higher quality. The timothy hay would not be suitable for a horse with sugar sensitivities even though the starch levels are well below the 35% limit to be considered a high starch diet. The oat hay has a low NSC number compared to its average value, this is a result of the plants being cut at an earlier stage of head development than is typical.
Even though it is available, the horse does not need a complete mineral supplement as it is only marginally deficient in phosphorous (P) as provided by the diet. Since this is a growing horse and the requirement for adequate levels of calcium (Ca) is critical it would be advised to provide a small amount of a calcium-phosphorous supplement. The horse is receiving the proper amounts of copper (Cu) and Zinc (Zn) but the ratio is on the low side for adequate absorption levels if there was a marginal amount provided of these minerals. The diet will need to be monitored to ensure that more than the required amount is maintained to allow for full absorption. While it appears to be deficient in iodine (I), the horse should be provided with an iodized salt block that is fed free choice and will provide for any iodine required. The horse may be deficient in Vitamins A, E, and D depending on the length of time since it had access to fresh forage or sunshine.
|Component||Timothy Hay||Oat Hay||Beet Pulp||Foal||Mineral||Required Amt||+/-|
|DM %||85.1 (84.4)||85.0 (85.0)||(91.738)||(90)||-||84-90||ok|
|Lignin %||5.3 (5.615)||4.0 (4.72)||(4.143)||-||-||<7?||ok|
|ADF %||25.3 (38.748)||34.2 (37.253)||(26.213)||-||-||<31-40||ok|
|NDF %||52.5 (62.350)||55.0 (58.826)||(41.156)||8.0||-||<50-53||ok|
|WSC %||22.2 (11.432)||12.3 (10.027)||(10.897)||92||-||10-17||ok|
|ESC %||12.0 (7.068)||10.0 (10.923)||(8.902)||-||-||-||-|
|Starch %||0.2 (1.649)||1.3 (0.987)||(0.992)||-||-||<35?||ok|
|NFC %||30.5 (19.538)||23.1 (25.187)||(44.908)||-||-||-||-|
|Fat %||2.3 (2.556)||2.6 (2.265)||(1.273)||5||-||<6, max 10||ok|
|Ash %||5.07 (7.832)||6.05 (7.136)||(7.334)||-||-||<12||ok|
|RFV||123 (89.368)||105 (96.429)||-||-||-||+100||ok|
|RFQ||152 (125.61)||137 (113.146)||-||-||-||110-115||Great|
|DE, Mcal/kg||2.47 (2.04)||2.29 (2.13)||1.165(2.63)||-||-||23.3(26.33)||+3.03Mcal|
|CP||12.0 (10.897)||15.7 (8.291)||(9.286)||16||-||1014g (1388)||+374g|
|Lysine||0.516(0.38)||0.675 (0.32)||(0.44)||0.688)||-||43.6g (59.7)||+ 16.1g|
|Ca||0.57 (0.489)||0.36 (0.301)||(1.017)||1.0||-||58g (59)||+ 1g|
|P||0.2 (0.239)||0.26 (0.203)||(0.089)||0.7||-||32g (30)||-2g|
|Calcium : Phosphorous Ratio 1.5-3:1||2.25:1||ok|
|Mg||0.15 (0.208)||0.23 (0.142)||(0.241)||0.2||1.6||6.21g (19.5)||+13.29g|
|K||1.94 (1.846)||1.75 (1.663)||(0.705)||(0.7)||-||19.4g (158.4)||+139.0g|
|Cl||0.71 (0.599)||1.33 (0.922)||(0.165)||(0.1)||-||30.1g (81.5)||+ 51.4g|
|S||0.21 (0.177)||0.23 (0.132)||(0.304)||-||0.50||22.5g (29.9)||+ 7g|
|Co (mg/kg)||(0.578)||(0.722)||(0.833)||3.6||30||0.4mg (11.3)||+ 10.9mg|
|Cu (mg/kg)||(8.575)||(7.545)||(8.908)||28||700||81mg (112.9)||+31.9|
|Zn (mg/kg)||(31.079)||(19.466)||(24.475)||136||4,000||323.8mg (428.3)||+104.5|
|Copper : Zinc Ratio 1:4-5||1:3.8||ok|
|I (mg/kg)||0||0||0||0.2||40||5.3mg (0.32)||-4.98|
|Mn (mg/kg)||(83.552)||(64.044)||(62.167)||75||2,100||323.8mg (732)||+408.2|
|Se (mg/kg)||(0.127)||(0.062)||(0.165)||0.5||15||0.81mg (1.64)||+0.83mg|
The Math if you are brave enough to determine all requirements yourself:
Note: all math calculations are based on the metric scale.
Horses can vary in the amount of feed that is required to maintain body weight so it is more beneficial to determine actual requirements of various
components based on amount fed rather than amount of work performed. If your horse consumes a higher amount of total feed per day than what is
generally estimated then use the appropriate higher category for calculations.
Maintenance, breeding stallion, pregnant mare, light exercise: 2% of body weight
Moderate exercise: 2.25% of body weight
Heavy exercise, growing horse, lactating mare: 2.5% of body weight
.....Where BW = bodyweight in kg
.....Where % eff = percent efficiency of absorption of the mineral source
.....Where ADG = average daily gain in kg
Energy/Calorie Requirement (DE):
Maintenance/easy keeper/Draft horse: DE (Mcal/d) = 1.4 + (0.0303 * BW)
Maintenance/average: DE (Mcal/d) = 1.4 + (0.0333 * BW)
Maintenance/hard Keeper: DE (Mcal/d) = 1.4 + (0.0363 * BW)
Light exercise: DE (Mcal/d) = (0.0333 * BW) * 1.20
Moderate exercise: DE (Mcal/d) = (0.0333 * BW) * 1.40
Heavy exercise: DE (Mcal/d) = (0.0333 * BW) * 1.60
Very heavy exercise: DE (Mcal/d) = (0.0363 * BW) * 1.90
Growing horse: De (Mcal/d) = (56.5X (superscript -0.145) * BW + (1.99 + 1.21X – (0.021 * X squared) * ADG.....Where X = age in months
Pregnant Mare, increases above maintenance:... at 8 months: + 11-19% ...at 9 months: + 13-21%...at 10 months: + 20 – 28%
Winters colder than -15C: add 2.5% more DE per degree colder for mature horses, add 1.3% more DE for growing horses
Protein (Crude) Requirement (CP):
Maintenance: CP (g/d) = 1.26g * BW
Light exercise: CP (g/d) = (1.26g * BW) + (0.089g * BW)
Moderate exercise: CP (g/d) = (1.26g * BW) + (0.177g * BW)
Heavy exercise: CP (g/d) = (1.26g * BW) + (0.266g * BW)
Very heavy exercise: CP (g/d) = (1.26g * BW) + (0.354g * BW)
Growing horse: CP (g/d) = (1.44g * BW) + ((ADG * 0.2)/E)/0.79
...where E= 0.50 for 4-6 months of age,
...where E= 0.45 for 7-8 months of age,
...where E= 0.40 for 9-10 months of age,
...where E= 0.35 for 11 months of age, and
...where E= 0.3 for 12 months of age and older
Pregnant mare, 5 months+: CP = (1.26g * BW) + ((fetal gain in kg/0.5)/0.79)
...Where fetal gain = 500kg horse 0.38kg/d after day 240
...Where fetal gain = 200kg Pony: 0.13kg/d after day 240
Lactating mare: CP = (1.44g * BW+ (50g * milk production (kg/d))
Lysine Requirement (Lys): Lys = BW * 0.54g
Or Lysine (g/d) = CP *4.3%
Vitamin A Requirement:
Maintenance: vit A = 30IU/kg BW
Working horse: vit A = 45IU/kg BW
Growing horse: vit A = 45IU/kg BW
Pregnant mare: vit A = 60IU/kg BW
Lactating mare: vit A = 60IU/kg BW
Vitamin B1 (Thiamin):
Maintenance: vit B1 = 0.06mg/kg BW
Light exercise: vit B1 = 0.06mg/kg BW
Moderate exercise: vit B1 = 0.0675mg/kg BW
Heavy exercise: vit B1 = 0.075mg/kg BW
Growing horse: vit B1 = 0.075mg/kg BW
Lactating mare: vit B1 = 0.075mg/kg BW
Vitamin B2 (Riboflavin):
Maintenance: vit B2 = 0.04mg/kg BW
Light exercise: vit B2 = 0.04mg/kg BW
Moderate exercise: vit B2 = 0.045mg/kg BW
Heavy exercise: vit B2 = 0.05mg/kg BW
Growing horse: vit B2 = 0.05mg/kg BW
Lactating mare: vit B2 = 0.05mg/kg BW
Vitamin D Requirement:
Mature horse (estimate): vit D = 6.6IU/kg BW
Growing horse, 0-6 months (estimate): vit D = 22.2IU/kg BW
Growing horse, 7-12months (estimate): vit D = 17.4IU/kg BW
Growing horse, 13-18 months (estimate): vit D = 15.9IU/kg BW
Growing horse, 19-24 months (estimate): vit D = 13.7IU/kg BW
Vitamin E Requirement:
Maintenance: vit E = 1IU/kg BW
Light exercise: vit E = 1.6IU/kg BW
Moderate exercise: vit E = 1.8IU/kg BW
Heavy exercise: vit E = 2IU/kg BW
Growing horse: vit E = 2IU/kg BW
Lactating mare: vit E = 2IU/kg BW
Calcium Requirement (Ca):
Mature horse: Ca (g/d) = 0.04g * BW
Growing horse: Ca (g/d) = (0.072g * BW) + (32g * ADG)
Pregnant mare,....At 6-7 months: Ca (g/d) = 0.056g * BW,....At 8-11 months: Ca (g/d) = 0.072g *BW
Phosphorous Requirement (P):
Maintenance: P (g/d) = 0.01g/% eff * BW
Light exercise: P (g/d) = (0.01g / % eff * BW) + (0.0028 / % eff * BW)
Moderate exercise: P (g/d) = (0.01g / % eff * BW) + (0.0049 / % eff * BW)
Heavy exercise: (0.01g / % eff * BW) + (0.0105 / % eff * BW)
Growing horse: P (g/d) = (0.018g / % eff * BW) + (8g / % eff * ADG)
Pregnant mare: at 6-7 months: P (g/d) = 0.0143g / % eff * BW
Pregnant mare: at 9-11 months: P (g/d) = 0.0186g / % eff * BW
Lactating mare, 0-3 months: P (g/d) = (0.01g / % eff * BW) + (0.032 * BW * 0.75g / % eff)
Lactating mare, 4-5 months: P (g/d) = (0.01g / % eff * BW) + (0.026 * BW * 0.5g / % eff)
Lactating mare, 5+ months: P (g/d) = (0.01g / % eff * BW) + (0.022 * BW * 0.5g / % eff)
Magnesium Requirement (Mg):
Maintenance: Mg (g/d) = 0.015g * BW
Light exercise: (0.015g * BW) + (0.004g * BW) or (0.019g * BW)
Moderate exercise: (0.015g * BW) + (0.008g * BW) or (0.023g * BW)
Heavy exercise: (0.015g * BW) + (0.015g * BW) or (0.030g * BW)
Growing horse: Mg (g/d) = (0.015g * BW) + (1.25g * ADG)
Pregnant mare: at 6-7 months: Mg (g/d) = (0.015g * BW) + (0.0002g * BW) or (0.0152g * BW)
Pregnant mare: at 9-11 months: Mg (g/d) = (0.015g * BW) + (0.0003g * BW) or (0.0153g * BW)
Lactating mare: 0-3 months: Mg (g/d) = (0.015g * BW) + (0.032g * BW * 0.23)
Lactating mare: 4-5 months: Mg (g/d) = (0.015g * BW) + (0.026g * BW * 0.23)
Lactating mare: 5+ months: Mg (g/d) = (0.015g * BW) + (0.020g * BW * 0.11)
Potassium Requirement (K):
Maintenance: K (g/d) = 0.05g * BW
Light exercise: K (g/d) = 0.05g * BW * 1.1
Moderate exercise: K (g/d) = 0.05g * BW * 1.4
Heavy exercise: K (g/d) = 0.05g * BW * 1.8
Growing horse: K (g/d) = (0.05g * BW) + (1.5g *ADG / 0.5)
Pregnant mare, 9-11 months: K (g/d) = 0.0517g * BW
Lactating mare: 0-3 months: K (g/d) = (0.05g * BW) + (0.032g * BW * 1.4)
Lactating mare: 4-5 months: K (g/d) = (0.05g * BW) + (0.026g * BW * 0.8)
Lactating mare: 5+ months: K (g/d) = (0.05g * BW) + (0.020g * BW * 0.8)
Maintenance: Na (g/d) = 0.02g * BW
Exercising Horse: Na (g/d) = (0.02g * BW) + (3.1g * BW lost during exercise)
Growing horse: Na (g/d) = (0.02g * BW) + (1.0g * ADG)
Pregnant mare, 9-11 months: Na (g/d) = 0.022g * BW
Lactating mare: 0-3 months: Na (g/d) = (0.02g * BW) + (0.032g * BW * 0.17)
Lactating mare: 4-5 months: Na (g/d) = (0.02g * BW) + (0.026g * BW * 0.14)
Lactating mare: 5+ months: Na (g/d) = (0.02g * BW) + (0.020g * BW * 0.14)
Maintenance: Cl (g/d) = 0.080g * BW
Exercising Horse: Cl (g/d) = (0.08g * BW) + (5.3g * BW lost during exercise)
Growing horse, 0-6 months: Cl (g/d) = (0.08g * BW) + (0.013g * BW), or 0.093g Cl * BW
Growing horse, 6-12 months: Cl (g/d) = (0.08g * BW) + (0.005g * BW), or 0.085g Cl * BW
Growing horse, 12-24 months: Cl (g/d) = (0.08g * BW) + (0.0025g * BW), or 0.0825g Cl * BW
Pregnant mare, 9-11 months: Cl (g/d) = 0.082g * BW
Lactating mare: 0-3 months: Cl (g/d) = (0.08g * BW) + (0.011g * BW), or 0.091g Cl * BW
Estimated as 0.15% of the diet on a dry matter basis
Maintenance: Cu (mg/kg) = 0.0002g * BW, or 10mg/kg of feed
Light exercise: Cu (mg/kg) = 0.0002g * BW, or 10mg/kg of feed
Moderate exercise: Cu (mg/kg) = 0.000225g * BW, or 11.25mg/kg of feed
Heavy exercise: Cu (mg/kg) = 0.00025g * BW, or 12.5mg/kg of feed
Growing horse: Cu (mg/kg) = 0.00025g * BW, or 12.5mg/kg of feed
Pregnant mare, 9-11 months: Cu (mg/kg) = 0.00025g * BW, or 12.5mg/kg of feed
Lactating mare: Cu (mg/kg) = 0.00025g * BW, or12.5mg/kg of feed
All horses: I (mg/kg) = 0.35mg/kg of feed
Pregnant mare, 9-11 months: I (mg/kg) = 0.4mg/kg of feed
Iron (Fe): not required to be supplemented
Mature horse: I (mg/kg) = 40mg/kg of feed
Growing horse: I (mg/kg) = 50mg/kg of feed
Pregnant mare: I (mg/kg) = 50mg/kg of feed
Lactating mare: I (mg/kg) = 50mg/kg of feed
Manganese (Mn): not generally required to be supplemented
All horses: Mn (mg/kg) = 40mg/kg of feed
All horses: Se (mg/kg) = 0.1mg/kg of feed
All horses: Zn (mg/kg) = 40mg/kg of feed
Omega-3 fatty acid (alpha-linoleic acid):
All horses: 0.5% x kg of feed
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