The objectives of this study were to examine the effect of supplying post-ruminal L-glutamine in mid-lactation Holstein dairy cows on plasma amino acid profile, dry matter intake, milk yield and milk composition. The experiment was designed as a 4 × 4 Latin square with four 2-wk periods. Cows were continuously infused post-ruminally with graded levels of L-glutamine (L-Gln) for 5 consecutive days during the second week of each period. During the last 24 h of the infusion, blood plasma was collected every 6 h for the determination of plasma amino acid concentrations. Plasma Gln concentration increased (P < 0.05) with increasing L-Gln daily infusions. Infusion of 0, 100, 200, and 300 g d–1 resulted in blood plasma Gln concentrations of 289.5, 299.2, 356.4 and 386.2 mmol L–1, respectively. The level of Gln infusion also resulted in a decrease in the blood plasma concentration of phenylalanine, but the concentrations of all other amino acids were not affected. The administration of Gln did not affect dry matter intake, milk yield and milk composition. Key words: Post-ruminal, L-glutamine, plasma amino acids, milk constituents
Rumen-Protected Methionine Fed to Dairy Cows: Bioavailability and Effects on Plasma Amino Acid Pattern and Plasma Metabolite and Insulin Concentrations
