Size does matter
SIZE DOES MATTER
So does how you achieve it? The growth of young horses has received much attention from the veterinary scientists and some clear results have come from this research.
Energy, protein and amino acid intake have the greatest impact on the growth and development of growing horses. Protein requirements of the growing foal are a function of the amino acid requirements of the foal.
Lysine has been shown to be the first limiting amino acid in the horse and threonine the second limiting amino acid. A limiting amino acid can be described as one that if not present will prevent protein from being made even if other amino acids are present in adequate quantities. Protein quality can be improved by supplementing with amino acids that if insufficient in the diet, are limiting or preventing protein synthesis.
Amino acids are the building blocks of protein. The quality of the protein is determined by its amino acid composition. It is the quality of the protein in the diet that regulates how well the horse grows and functions.
It is accepted that in growing horses, energy and protein are usually the first and second limiting factors in the diet. Increasing protein quality rather than quantity has the advantage of more efficient utilisation by the horses; however it is not good practice to create excessive inputs of energy and high quality protein due to the risk of extreme growth rates and creation of developmental disorders.
E.A OTT research ( Energy, Protein and Amino Acid Requirements for Growth of Young Horses ) shows that reduction of concentrate protein and subsequently the feed intake of the animal, decreases the blood insulin concentrations which may be advantageous in helping minimise bone development problems. He goes on to suggest that protein concentrate can be reduced when the diet is proportionately supplemented with Lysine and still support maximum growth response.
Research data such as “Growth of thoroughbreds fed a low protein supplement fortified with Lysine and Threonine W.B. Staniar et al) concludes that fortifying the diet with lysine and threonine , improves protein quality and enables full realisation of genetic potential for growth, while raising horses on forages with a lower protein concentration.
In addition research has shown that horses in work, strenuous exercise , benefit from lower protein concentrate and lysine threonine supplementation . Heat production from higher levels of protein may interfere exercise by attenuating fatigue ( Kronfeld) and an increased acidity will interfere with glycolysis and muscle fibre contraction ( Mainwood and Reynaud) , ie restriction of dietary protein may be beneficial during strenuous exercise by diminishing production of heat and acid. (P.M. Graham-Thiers et al).
In conclusion dietary protein can be reduced , and in doing so reduce negative effects, without loss of growth or performance, if the diet is then supplemented with lysine and threonine.