Whole-body protein and glucose metabolism in cows fed diets with varying amino acid supply under heat stress

Citation

Ruiz-González, A., Y. H. Leung, A. Celimin, A. Kenez, P. Y. Chouinard, R. Gervais, D. R. Ouellet, H. Lapierre, and D. E. Rico. 2022. Whole-body protein and glucose metabolism in cows fed diets with varying amino acid supply under heat stress. J. Dairy Sci. 105, Suppl. 1, Page 93.

Résumé en langage clair

Supplementation of Lys, Met, and His may be needed to meet lactation requirements while dairy cows ingest lower amounts of MP under heat stress. Twelve Holstein cows were used to test the effect of balancing Lys, Met, and His supply on whole-body (WB) protein and glucose metabolism. Three treatments were tested with 14-d periods: 1) heat stress (HS; temperature-humidity index (THI) 82; 17% crude protein (CP); estimated supply from d7–14 (g/d): 107 Lys, 34 Met, 37 His, and 1715 MP), 2) pair feeding in thermoneutrality (PF; THI 64; 17% CP; amino acids (AA) and MP supply equal to HS) or 3) HS with increased AA supply (HS+AA; THI 82; 17% CP; in g/d 178, 64, 43 and 1730 of Lys, Met, His, and MP, respectively). Using stable isotopes of NaHCO3, L-Leu and glucose, infused into a jugular vein over 4-h, WB kinetics of protein and glucose were estimated. Heat stress reduced dry matter intake and milk yield by 34% and 40% from d0 to d7. The WB rate of appearance (Ra) of Leu was not affected by treatment, but its fractional oxidation (FO) increased in HS by 31% relative to PF cows (P = 0.02), whereas Leu FO decreased by 29% in the HS+AA group relative to HS (P = 0.02). Leu used for protein synthesis and secreted in milk protein decreased in HS by 13%, 16%, respectively, relative to PF cows (P < 0.05), but was not affected by AA supply. The glucose WB Ra did not differ across treatments (P = 0.11), although glucose concentrations tended to be lower (−5%, P = 0.06) in HS relative to PF. These results show that HS impairs protein metabolism in cows and that increasing Lys, Met and His supply did reduce Leu, and likely other AA, oxidation during HS conditions.

Résumé

Supplementation of Lys, Met, and His may be needed to meet lactation requirements while dairy cows ingest lower amounts of MP under heat stress. Twelve Holstein cows (42.2 ± 10.6 kg milk/d; 83 ± 28 DIM) were used to test the effect of balancing Lys, Met, and His supply on whole-body (WB) protein and glucose metabolism in a split-plot design, with parity as the main plot (multiparous n = 6; primiparous n = 6). Within each parity, 3 treatments were tested in a replicated 3 × 3 Latin square with 14-d periods: 1) heat stress (HS; THI 82; 17% CP; estimated supply from d7–14 (g/d): 107 Lys, 34 Met, 37 His, and 1715 MP), 2) pair feeding in thermoneutrality (PF; THI 64; 17% CP; AA and MP supply equal to HS) or 3) HS with increased AA supply (HS+AA; THI 82; 17% CP; in g/d 178, 64, 43 and 1730 of Lys, Met, His, and MP, respectively). On d 12, [13C] NaHCO3 (1.96 mmol/h) and on d13, 1[13C] L-Leu (3.38 mmol/h) and 6,6[2H2] glucose (24.5 mmol/h) were infused into a jugular vein over 4-h. Blood samples were collected from the contralateral jugular vein every 25 min during the last 2 h of the infusion to measure CO2, Leu and glucose isotopic enrichments and calculate WB
kinetics. The statistical model included the random effects of cow and period, and the fixed effects of parity, treatment, and their interactions. No parity × treatment interactions were detected. Heat stress reduced
DMI and milk yield by 34% and 40% from d0 to d7. The WB rate of appearance (Ra) of Leu was not affected by treatment, but its fractional oxidation (FO) increased in HS by 31% relative to PF cows (P = 0.02), whereas Leu FO decreased by 29% in the HS+AA group relative to HS (P = 0.02). Leu used for protein synthesis and secreted in milk protein decreased in HS by 13%, 16%, respectively, relative to PF cows (P < 0.05), but was not affected by AA supply. The glucose WB Ra did not differ across treatments (P = 0.11), although glucose concentrations tended to be lower (−5%, P = 0.06) in HS relative to PF. These results show that HS impairs protein metabolism in cows and that increasing Lys, Met and His supply did reduce Leu, and likely other AA, oxidation during HS conditions.

Date de publication

2022-06-19

Profils d'auteurs