Nutrition Bulletin: Feeding the Performance Horse

By Dr. Les Breuer, Ph.D.

Feeding practices in race horses and other horses involved in various athletic activities are extremely variable. There is some logic for this because individual horses are being trained for different types of performance and they vary in their size and in the way they respond to training and exercise. They also have their idiosyncrasies in eating behavior and feed preferences. Therefore, it isn't surprising that horse trainers will have many different opinions on ways of taking care of these needs. Many of these practices are very effective but some are not likely to be beneficial to the horse and some may even be detrimental.

There are some important nutritional considerations in feeding horses involved in athletic activities that can be derived from understanding the physiological processes taking place in these horses. The purpose of the following discussion is to identify some of the more important nutritional principles involved from information available from research and practical observations.

There are five classes of nutrients that must be considered in feeding performance horses or any other type of horse. These are water, energy, protein, minerals and vitamins. These are ranked in their importance by total amount needed in the diet.

Water

Water is an extremely important nutrient to consider in feeding performance horses. Non-working horses under comfortable environmental conditions need two to three units of weight (pounds or kilograms) of water for every unit of dry feed consumed. The total amount of water needed increases dramatically when horses sweat due to high temperatures and humidity, especially when combined with hard work. These water losses must be replaced. Electrolytes (primarily sodium and potassium) are also lost when horses sweat profusely. These electrolyte losses have to be replaced by oral dosing or addition to the feed or water.

Some horses become non-sweaters in areas with very high environmental temperatures and humidity. Special care should be taken in these areas to furnish adequate water and electrolytes. Even when such precautions are taken, some horses still develop the condition, apparently because of a dysfunction of the sweat glands. Moving to a cooler climate or housing in air-conditioning will usually reverse the condition.

Horses consuming feeds such as alfalfa hay with high levels of protein and minerals will also have increased urinary and fecal water losses. The extra urination and sweating connected with ingesting such feeds may be detrimental to performance, especially when horses are already under heat stress. Therefore many trainers prefer to feed hays with low alfalfa content or only grass hay.

As horses become progressively dehydrated from inadequate water intake, athletic performance will decline and the horses will decrease their feed intake. Eventually, blood tests will indicate that the horses are dehydrated. If a scale is available, weight losses may also indicate that horses are dehydrated. Changing water sources, adding flavors to water, and feeding bran mashes are some methods used to increase water intake in horses.

Protein

Protein is an important nutrient in the diet of any horse but in contrast to some other species, protein does not appear to have a specific function related to athletic performance in horses. Most performance horses today receive diets containing at least 10-12% protein. Such levels should be adequate for development of additional muscle mass in horses in training as well as maintaining muscle mass in fit horses provided the diet contains some high quality protein with a good amino acid balance. It is not advisable to feed excessive amounts of protein because of the extra burden placed on the horse's metabolism to break down and excrete the excess protein.

Minerals

Minerals such as calcium, phosphorus, magnesium, potassium and salt (NaCI), as well as trace minerals such as iron, copper and selenium all have either direct or indirect involvement in physiological processes taking place in performance horses. They should all be supplied in the diet as part of a balanced grain feed or as supplements added to the grain ration. Very few studies have been conducted with horses on the quantitative requirements of minerals for athletic performance. The amounts and balances of minerals recommended for feeding to growing and developing horses appear to be adequate for performance horses. There is no good evidence, theoretical or practical, to support the practice of feeding high levels of trace minerals to normal healthy performance horses. As discussed above, supplemental electrolytes should be provided when horses lose large quantities of electrolytes in sweat.

Vitamins

Vitamins such as Vitamin A, D and E and many of the B Vitamins have either direct or indirect involvement in the metabolism of performance horses. Vitamin E, thiamine and folic acid may have special roles in the metabolism of performance horses. All of the vitamins are required for the general health and physical condition of horses and also have other important effects such as appetite stimulation and blood building. Even though much of the requirement for vitamins will be supplied by natural ingredients in the diet or by synthesis by bacteria in the large intestine, their adequacy in the diets of performance horses should be assured by addition through a balanced feed or by nutritional supplements. Again, as in the case of trace minerals, once the requirement for a vitamin is met, nothing is gained by adding multiple supplements of the vitamin to the diet of a performance horse.

Energy

"Energy" differs from other nutrients in that it can be furnished by a number of organic compounds that serve as fuels for metabolic processes. This includes the process of muscle contraction that is the basis for the locomotion involved in all athletic performances in horses. There are two very important considerations about the effect energy has on performance. One is that the total amount of energy consumed as measured by total calories taken in must be adequate to satisfy the work load created by the athletic performance with enough left over to maintain the muscle mass and body condition of the horse. The second consideration is that the different sources of energy can have "extra caloric" or special effects on the ability of the horse to perform. These special effects may be positive or negative in helping the horse perform up to the maximum allowed by its bred-in potential, training, physical fitness and soundness.

The naturally occurring fuel sources in feeds include fiber found primarily in hay or pasture, proteins, starches, sugars and fats or oils. On a caloric basis, one weight unit (pound or kilogram) of fat is the equivalent of nearly three units of oats and five or six units of hay or pasture. The difference in calories per unit volume is even more dramatic. Many horses involved in intense athletic competition require 30,000-40,000 calories per day and they may have difficulty taking in enough calories to perform and stay physically fit due to limitations in appetite and digestive capacity. Therefore, it is necessary to feed relatively large amounts of grain with its higher caloric density to meet the energy requirement of performance horses. Fats and oils with an even higher caloric density than grain can be used to help meet the energy requirement and reduce the risk of problems that may occur from very high grain intakes.

Research with horses has established that fats and oils can have special, "extra caloric" effects on energy metabolism in horses. Adding fat to a performance horse diet may result in an increase in glycogen storage in muscle. Dietary fat may also help horses maintain higher blood glucose levels by protecting or conserving glycogen. Dietary fat may train the horse’s metabolism to use body fat stores at lower oxygen levels than is the case when horses are fed diets with no added fat. Such effects could have important implications on the ability of a horse to perform by conserving the body’s reserves of glucose (glycogen) to be utilized late in a performance event thereby improving performance by delaying the onset of fatigue. These theories have been supported experimentally using high-speed treadmills and by measuring levels of blood glucose and blood lactate during exercise.

Feeding Management

Because of the very large energy requirement of performance horses, it is critically important that horses have the appetite and capacity to consume the quantity of feed needed to supply their energy requirement. Therefore, in the case of performance horse feeds, it is equally important that a feed meet palatability requirements as well as meet nutritional standards.

Feeding hay and grain should be timed to not interfere with optimal performance. Hay feeding should be restricted and timed in the case of horses involved in intense athletic events so they do not have an unnecessary weight handicap caused by excessive gut fill of undigested hay residue and water. On the other hand, horses performing in less intense events over longer periods of time where water and electrolyte losses may limit performance may benefit from the higher gut fill resulting from hay feeding. Other performance benefits may be gained by not feeding grain for several hours before intense exercise so that there is little or no small intestinal absorption and tissue storage of nutrients taking place.