Effect of concentration of some dietary amino acids and protein on plasma urea nitrogen concentration in growing kittens.

The effect of various levels of leucine, isoleucine, tryptophan, histidine and phenylalanine with and without tyrosine in isonitrogenous purified amino acid-based diets on plasma urea nitrogen (PUN) of growing kittens was examined. In addition, the effect of various levels of nitrogen supplied as amino acids or as a mixture of amino acids and protein on PUN was measured. PUN was not a useful predictor of the concentration of an amino acid that maximized either growth or nitrogen balance. Intake of nitrogen was highly correlated with PUN and accounted for 96% of the variation in PUN.