Effect of intraperitoneal amino acids on nitrogen balance and plasma amino acids in calves.

Abstract

Six young Holstein bull calves were used to evaluate responses to IP administrations of amino acids in terms of nitrogen balance parameters and plasma amino acids. A mixture of methionine, lysine, tryptophan, histidine and arginine appeared to improve nitrogen balance (P<.10) as compared to a mixture of the remaining essentials (as defined for the rat) when both were supplemented with glycine or to a saline control. When the constituent amino acids in the first group (with the exception of tryptophan) were administered singly to three calves, nitrogen balance was not improved. Short-term plasma amino acid responses were rather variable; however, plasma lysine, methionine and histidine were consistently depressed following IP administration of nonspecific sources of amino nitrogen. The depressing effect of intraperitoneally administered nonspecific nitrogen on the plasma levels of lysine, methionine and histidine suggest that these may be the first-limiting essential amino acids after the nonspecific nitrogen requirements are met. While no single amino acid could then be definitively identified as limiting for calves in this study, the evidence suggests a group of amino acids may be equally limiting.