Skip to content
Search Library
thumbnail

Horses derive energy from various components of their diets, namely starch, fat, fiber, and protein. An idle mature horse likely obtains most of his dietary energy from fiber-rich feedstuffs such as pasture and hay. Fiber is fermented in the hindgut and energy created for maintenance of body processes. For horses involved in regular athletic activity, a fiber-only diet will probably not provide enough fuel for the combined toll of exercise and maintenance of body weight, so other energy sources must be added. Of those others mentioned previously—starch, fat, fiber, and protein—protein is least efficient at fueling work.

If the protein intake of a performance horse exceeds its requirement, the superfluous protein can be used as a source of energy. The amino acids from the extra protein are broken down by the liver, and the carbon skeletons that are left are oxidized to produce adenosine triphosphate (ATP), the molecule used to power muscular activity, or used to make glucose or fat. The nitrogen from the protein is excreted in the urine as urea and changed to ammonia as it interacts with environmental microorganisms.

Forages, cereal grains, and seed meals all contribute to the basic protein requirements of performance horses. “Forages are excellent sources of protein and amino acids, though the type of forage will determine protein quantity. Alfalfa (lucerne), lespedeza, and varieties of clover are the most commonly fed legumes, and crude protein concentration of these is near 18-20% on a dry matter basis,” said Kathleen Crandell, Ph.D., a nutritionist with Kentucky Equine Research (KER).

Generally, grasses are lower than legumes in crude protein, containing 5-15% crude protein on a dry matter basis. Typical grasses include orchardgrass, Kentucky bluegrass, tall fescue, and timothy. “Stage of growth affects crude protein content, as crude protein peaks when plants are in the vegetative stage and is lowest in late maturity. By and large, factors that affect total protein concentration will also influence amino acid concentrations in the forage,” explained Crandell.

Cereal grains, which are primary ingredients in typical commercial concentrates, supply horses with some protein: oats have 13% crude protein; barley, 12%; and corn, 9%. The protein in cereal grains is not considered high quality, meaning grains might not have an optimal complement of amino acids.

Various byproducts, typically called seed meals, provide high-quality protein to horses. Soybean meal, about 48% crude protein, is the most widely used seed meal because of its availability and desirable amino acid profile. Seed meals with lower lysine content include canola, cottonseed, sunflower, safflower, and peanut meals, and while these can be used in concentrates, additional amino acids would likely be added to the formulation for optimal protein delivery, according to Crandell.

Excessive protein should be avoided in the exercised horse for several reasons: (1) water requirements increase with excessive protein intake, and dehydration might become a concern if water is not offered; (2) urea levels increase in the blood, leading to greater urea excretion into the gut, which may increase the risk of intestinal disturbances; (3) the breakdown of protein produces more internal heat than the breakdown of other nutrients for energy, which can be a problem when exercising in heat and humidity; (4) increased ammonia in the environment from the urea excretion in the urine may have a harmful effect on respiratory tissues; and (5) protein is an expensive energy source, so feeds with higher protein often cost more than traditional formulations.

Energy requirements are best served by a medley of energy sources. Some performance horses are sensitive to starch so must rely upon fat and fermentable fiber. While protein is important for muscle health and repair, as well as a host of other body-wide processes, it should not be considered a primary energy substrate for performance horses.

X

Subscribe to Equinews and get the latest equine nutrition and health news delivered to your inbox. Sign up for free now!