Effect of Abomasal Administration of Lysine and Methionine or Lysine Alone on Nitrogen Balance and Plasma Free Amino Acid Concentrations in Early-Weaned Calves Fed a Corn and Soybean Meal Diet

A total of 24 Holstein bull calves were used in two nitrogen (N) balance trials, both of which consisted of duplicate experiments using 6 calves eachin a 2×2 Latin square design with three replicates and 2wk-period. The calves were weaned at 6wk of age and trained to maintain reflex closure of the esophageal groove throughout the experiments started from 8wk of age. They received a basal ration consisted of corn, soybean meal and rice straw in every experiment, and N balance and plasma free amino acid concentrations were compared between two treatments: one was the administration of L-lysine monohydrochloride (L-LysHCI) with (Trial 1) or without (Trial 2) DL-methionine (DL-Met) through the esopgageal groove, and another was that of isonitronenous L-glutamine (L-Gln) as a control. As a result, N-balance was improved by the abomasal administration of L-LysHCl with DL-Met over the control, but not by that of L-LysHCl alone. The administration of both L-LysHCl and DL-Met increased plasma concentrations of free Lys and Met, but decreased those of branched chain amino acids (BCAA). On the other hand, the administration of L-LysHCl alone increased plasma Lys concentration without a significant effect on plasma BCAA concentrations.