Amino Acids For Horses-Triple Crown Discusses Their Relationship To Equine Protein

Protein is a source of amino acids for horses, not calories!
by Amy M Gill, PhD

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Protein is added to equine diets to provide amino acids so that the horse can make other proteins in its body. It is not added to be used as an energy or calorie source. This is a major misconception in the horse world. Energy is calories and in horse feeds, carbohydrates and fats are the main sources. Energy or calories are needed to drive the biochemical process of making protein, as well as many other processes such as muscular contraction and basic metabolic functions. Protein content or percentage should not be used to judge the caloric density of a feed or how “hot” a horse feed is. Horses get “hot” or excited from many variables including but not limited to stress, being fed too much starch and sugar, being confined to stalls and not getting enough exercise, but not from being fed the correct amount of protein in their diets. Also, protein is not the cause of developmental problems in growing horses: rapid growth rates from excessive caloric intake, particularly from starch, nutrient imbalances such as too little protein or minerals and genetic predisposition are all factors in orthopedic disorders. Deliberately restricting protein intake, as with any essential nutrient, is counterproductive when attempting to correct growth, metabolic or exercise related disorders. Not providing enough protein to any animal simply retards proper development or maintenance of body tissues.

Protein comes in many different forms and it is important that the type used in horse feed provides amino acids that the horse can use. For example, cows can use feathers as a source of protein because the microorganisms in the rumen are capable of degrading the protein and liberating nitrogen, but horses have no such mechanism in their stomachs. A cow feed with the source of protein as feathers might guarantee protein at 12% which is accurate for a cow, but the same feed would be protein deficient for a horse. Source of protein is very important! Typically, soybean meal is used as the protein source in horse feeds because the amino acids it contains meets the requirement of the horse very well. There is no risk of causing cancer when feeding soy to horses and some unsubstantiated anecdotal reports have claimed. Milk proteins are also very available but adult horses cannot tolerate high levels of milk products in the diet as they are lactose intolerant. Steer clear of any product that uses meat or fish meal products as a protein source for horses (fish oil for the purpose of supplying Omega 3 fatty acids can be fed to horses). Not only are they less digestible but also very unpalatable.

Another source of misinformation related to the feeding of horses is about the relationship between carbohydrate level and caloric content of feedstuffs. Carbohydrates come in two forms, insoluble such as fiber from hay and soluble such as starch and sugars from grains. Testing feedstuffs for soluble carbohydrates to determine which feeds are acceptable to be fed to horses with metabolic imbalances has become more common. Please be aware that the level of soluble carbohydrate in a feed does not equate to the caloric content of the feed. For example, a feed with 45% soluble carbohydrate is considered fairly high in starches and sugars, but this number tells nothing about the number of calories the feed contains. Soluble carbohydrate level and caloric content are two separate analyses and do not relate to each other at all.

Equine nutritionists don’t really even worry about the “crude protein” content of the feed anymore. The main concern when formulating a ration is for meeting the amino acid requirements. So don’t get hung up on protein – it is a vital and required component of the diet that when fed correctly is simply used by the horse to make other proteins.