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Effects of glucose and acetate infusion on mammary uptakes of essential amino acids by lactating dairy cows.

B. Li



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Effects of glucose and acetate infusion on mammary uptakes of essential amino acids by lactating dairy cows.
B. Li*1, R. Laforest1, L. Wright1, J. Kim1, P. Kedzierski1, V. Osborne1, J. Doelman1,2, J. Cant1. 1University of Guelph Guelph, ON, Canada, 2Trouw nutrition Putten, the Netherlands.

Previous research suggests that glucogenic energy can stimulate milk protein yield of dairy cows while lipogenic energy does not. To explore differences in mammary essential amino acid (EAA) utilization between these types of energy, 5 rumen-fistulated cows were given additional glucose or acetic acid in a 5 � 5 Latin square design. Infusion treatments were: 1) 10 L/d ruminal water (CTL), 2) 1.1 kg/d (LoG) or 3) 2.2 kg/d (HiG) abomasal glucose, and 4) 1.25 kg/d (LoA) or 5) 2.5 kg/d (HiA) ruminal acetic acid. Acetic acid and glucose infusion rates were isocaloric at low and high levels, respectively. Milk yields were recorded daily and milk samples were collected on the last 3 d of each 7-d infusion period. Tail and mammary venous samples were collected on d 7 to estimate mammary uptakes. Plasma samples for each cow were pooled over time by period. Plasma AA concentrations for each time point were analyzed using Ultra Performance Liquid Chromatography in conjunction with Empower Chromatography Data Software (Waters Corporation, Milford, MA). Linear contrasts of glucose and acetic acid dose were estimated by ANOVA assuming fixed effects of period and treatment, and random effects of cow. Glucose infusion had no effect on DMI (P = 0.97) or milk protein yield (P = 0.15) but increased lactose yield (P = 0.03) and tended to increase milk yield (P = 0.07). Acetic acid infusion dramatically decreased DMI from 18.8 kg/d on CTL to 13.8 and 14.9 kg/d on LoA and HiA respectively. Milk yield decreased 5.4 kg/d, protein yield decreased 201 g/d and lactose yield decreased 224 g/d on HiA compared with CTL (P ≤ 0.01) due to the decrease of DMI. Glucose infusion decreased arterial concentrations of all EAA (P < 0.01) except Met and Thr, but increased mammary plasma flow (MPF) rate (P < 0.01), so that mammary uptakes of EAA were not affected (P > 0.16). In contrast, acetic acid infusion increased concentrations of Ile, Leu, and Val (P < 0.08) without affecting other EAA concentrations (P > 0.20), had no effect on MPF (P = 0.70), and decreased mammary uptakes of Arg, Ile, Leu, and Phe (P < 0.10). Findings suggest that exogenous glucose encouraged milk protein production despite reduced plasma concentrations of some EAA, while exogenous acetic acid discouraged milk protein yield thereby increasing concentrations of some EAA.

Keywords: cow, amino acid, milk protein.

Biography: My name is Boning Li and I am a current PHD student at Animal Bioscience department in University of Guelph. I focused on effects of glucose and acetate infusion on mammary uptakes of essential amino acids on lactating dairy cows. Now I am mainly working on the effects of different amino acids on milk protein synthesis through cell culture. I will move this research into in vivo step by working with mouse and cows in the future.