Journal Article

Mammary Uptake, Portal-Drained Visceral Flux, and Hepatic Metabolism of Free and Peptide-Bound Amino Acids in Cows Fed Steam-Flaked or Dry-Rolled Sorghum Grain Diets

Simas, J., DeYoung, D., Bittar, C.M.M., Huber, T., Santos, F., Cuneo, P., Santos, J.E.P., Webb, K., Lozano, O., Alio, A., Tagari, H., Sadik, M., Nussio, L., Delgado-Elorduy, A., Theurer, B.

2008

Overview

Our objectives were to measure net fluxes of free AA (FAA) and peptide-bound AA (PBAA) across portal-drained viscera, liver, splanchnic tissues, and mammary tissues, and milk AA output of lactating Holstein cows (n = 8, 86±8 d in milk). Cows were fed an alfalfa-based total mixed ration containing 40% steam-flaked (SFS) or dry-rolled (DRS) sorghum grain. The total mixed rations were offered at 12-h intervals in a crossover design. Blood samples were obtained from indwelling catheters in portal, hepatic, and mammary veins and from mesenteric or costoabdominal arteries every 2h from each cow and diet. Intake of dry matter was 17.9 and 18.6 kg/d of the SFS and DRS diets, respectively, but dropped to 16.3 kg/d for cows fed the SFS diet in the last 3 experimental days, sampling day included. Milk and milk crude protein yields (kg/12-h sampling) were 13.85 vs. 13.25 and 0.425 vs. 0.396 for cows fed SFS or DRS, respectively, and were not affected by the considerable drop in dry matter intake of cows fed the SFS diet during the last 3 experimental days. The portal-drained visceral flux of total essential FAA was 417 and 442 g/12h (SEM 63) in cows fed SFS and DRS, respectively. However, the portal-drained visceral flux of 7 essential PBAA out of the 9 determined was numerically greater in cows fed the SFS diet, and total essential PBAA in that treatment was 77.4±22.2 compared with 35.4±50.2 g/12h for cows fed the DRS diet. This phenomenon was again observed in a greater total splanchnic flux (FAA + PBAA) of 462 and 371 g/12h in SFS- and DRS-fed cows, respectively. Mammary uptake of essential AA from both pools (free and peptide bound), and recovery of essential AA in milk, was again numerically higher in SFS-fed cows. In addition to FAA, quantifying the contribution of PBAA may improve our understanding of tissue use of AA substrates, and this may ultimately lead to improved diet formulations with respect to intestinal absorption and mammary uptake of AA.

• Publisher: Elsevier Inc,American Dairy Science Association,Am Dairy Sci Assoc
• Subject: amino acid / Amino Acids / Amino Acids - pharmacokinetics / Animal Feed / Animal productions / Animals / Biological and medical sciences / blood supply / Cattle / Cattle - metabolism / Cereal and baking product industries / cow feeding / cows / Cross-Over Studies / dairy cow / dry-rolled sorghum grain / Female / flaked sorghum / flakes / Food industries / free amino acids / Fundamental and applied biological sciences. Psychology / grain sorghum / Hepatic Veins / Hepatic Veins - physiology / Holstein / Intestinal Absorption / Intestinal Absorption - physiology / Lactation / Liver / Liver - blood supply / Liver - metabolism / liver function / mammary glands / Mammary Glands, Animal / Mammary Glands, Animal - metabolism / metabolic studies / metabolism / Milk / Milk - secretion / Milk Proteins / Milk Proteins - metabolism / nutrition physiology / peptide / peptide-bound amino acids / pharmacokinetics / physiology / portal vein / Portal Vein - physiology / portal-drained visceral fluxes / Random Allocation / rolling / ruminant nutrition / secretion / Sorghum / splanchnic tissues / steam-flaked sorghum grain / Terrestrial animal productions / Vertebrates