Effects of dietary excesses of the branched-chain amino acids on growth, food intake and plasma amino acid concentrations of kittens

The effect of excesses of the branched-chain amino acids (BCAA), particularly leucin, on growth, food intake and plasma amino acid concentrations were investigated in kittens. Effects of excess leucine were tested in kittens fed five basal diets that varied in their nitrogen and amino acid contents. Compared to rats, kittens were much less sensitive to excesses of the BCAA. Addition of 10% leucine to basal diets that provided nitrogen just at or below the minimal requirement of kittens resulted in no change or increased growth and food intake of kittens when the isoleucine and valine concentrations in the basal diet were just at or slightly in excess of the kitten's minimal requirements for those amino acids. An adverse effect of leucine added to low nitrogen basal diets was observed only when isoleucine and valine were provided below the kitten's requirement (80% of requirement). When basal diets containing adequate nitrogen (24% amino acids) were tested, the addition of leucine (10%) resulted in an adverse effect when isoleucine and valine were provided at 80% of the kitten's requirement and in mild growth depressions when isoleucine and valine were provided at 1.1 times the requirement. Leucine-induced growth depression was alleviated by the addition of isoleucine and valine at 0.5%, indicating that excess leucine caused a BCAA antagonism or an amino acid imbalance. With the addition of leucine to the basal diets, there were consistent decreases in concentrations of alanine and tyrosine in plasma but no consistent depressions in the concentrations of isoleucine and valine.