Valine

An essential amino acid, molecular weight (117.2) found in protein. Valine is one of the three branched-chain amino acids (with leucine and isoleucine). It is purely gluconeogenic, yielding propionate as an end-product of catabolism. The first two enzymatic reactions involved in valine catabolism use the same enzymes that catabolize leucine and isoleucine. The first reaction involves transamination, primarily in muscle. This produces the keto analogue, ketoisovaleric acid. This is then oxidatively decarboxylated, primarily in liver, by branched-chain keto acid dehydrogenase to the CoA derivative. After lysine, which is first limiting in low-protein maize–soybean meal diets, valine is among the next limiting amino acids (along with one or more of tryptophan, threonine and methionine) for young pigs, chickens and turkeys. A deficiency of valine amino acids in poultry can have a negative impact on growth, feather quality, feed efficiency, immune function, and reproductive performance. It is therefore important to ensure adequate levels of valine are included in poultry diets to support optimal health and productivity.