Protein content in horse feed have been the blame for several health and behavioural problems, however research has shown that this essential nutrient has more pros than cons, than originally thought. Higher protein feeds are often associated with higher starch levels. Research has shown that in fact it is the increased starch levels that can result in health and behavioural problems such as colic, laminitis and excitability.
What is Protein?
Protein is essential for growth, repair, muscle forming, tissue, enzymatic and endocrine function. After water it is the most vital nutrient the body needs, in fact 80% of fat-free, moisture free, body composition is protein.
Protein is made up of amino acids, the building blocks of the body, there are 21 amino acids with 10 classified as essential amino acids which must be supplied within the diet as they can not be synthesised by the horse. The main essential amino acid is lysine, vital for growth and nitrogen balance and often the most deficient within a forage-based diet. A study showed horses fed a deficient diet of lysine had a slower growth rate even when the percentage of crude protein was the same in both diets.
When designing a balanced diet, it is important sufficient quantities of these amino acids are present, this is known as a high-quality protein source. Soyabean meal is widely used for its desirable amino acid profile and is the highest source of crude protein at 48%. Another legume source, alfalfa has the ability to “fix” nitrogen from the atmosphere, recently alfalfa is being used more commonly as a protein source in horse’s diets.
Protein to Energy Ratio
Protein and energy should always be considered together when designing a diet especially for growing horses. A deficiency in the ratio will result in a decrease in growth rate contributing to further bone development issues. An excess in protein along with inadequate energy requires protein oxidase to produce more energy, which is consequently an expensive source of energy for the horse. Amino acids aid growth and repair, however without the energy the protein can not be synthesised correctly.
Excessive protein in the diet should be avoided for several reasons;
- An increase in water intake, if sufficient water is not supplied dehydration is likely to occur.
- Urea levels within the blood increases, resulting in an increase in urea excretion into the gut and therefore increases the risk of gastrointestinal disturbances.
- Protein digestion generates heat, this excessive heat is not desirable in performance horses.
- An increase in ammonia in the stabled environment which has been shown to causes detrimental effects to the respiratory tract.
Deficient in Protein
Protein is vital for body functions, therefore if there is a deficiency it can result in serious health problems. Some clinical signs include a rough coat, decrease in hoof growth, skeletal abnormalities in youngstock and a decrease in milk production in lactating mares.
Protein in the Performance Horse
As the work level increases the level of protein increase is only very slight despite what was once thought. Performance and racing horse feeds are often around 14% protein, this is usually to compensate the decrease in forage intake, it is also beneficial for young horses in training that are still growing.
“While protein in 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”