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Effects of heat stress and OmniGen-AF on physiological and inflammatory responses of mid-lactation dairy cows to intravenous lipopolysaccharide infusion.

T. N. Marins

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06-24-2020

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Abstract:

W59
Effects of heat stress and OmniGen-AF on physiological and inflammatory responses of mid-lactation dairy cows to intravenous lipopolysaccharide infusion.
T. N. Marins*1, J. Gao1, Q. Yang1, R. M. Binda1, C. M. B. Pessoa1, R. M. Orellana1, J. K. Bernard1, M. Garcia2, D. J. McLean2, J. D. Chapman2, D. J. Kirk2, S. Tao1. 1University of Georgia Tifton, GA, 2Phibro Animal Health Corp Teaneck, NJ.

Our aim was to evaluate hormonal and cytokine responses of mid-lactation Holstein cows fed OmniGen-AF (OG; Phibro Animal Health) or not with or without evaporative cooling to an intravenous lipopolysaccharide bolus (ivLPS) during summer. Multiparous cows (n = 60) were blocked by parity and DIM, and randomly assigned to 4 treatments (TRT) in a 2 � 2 factorial arrangement with 2 environments (E): cooled (CL) using fans and misters or non-cooled (NC), and 2 top-dressed feed additives (D, 56 g/d): OG or placebo as control (CON). All cows were cooled and fed respective diets for 60 d before experiment. At d 52 of the experiment, a subset of cows (n = 6/TRT) was iv-injected with LPS (0.20 μg/kg of BW). Blood collected at −1, −0.5, 1, 2, 3, 4, 6, 8, 12, 18 and 24 h relative to ivLPS were analyzed for cortisol (COR), prolactin (PRL), tumor necrosis factor (TNF) α and interleukin (IL) 10. From d −1 to 2 of ivLPS, daily DMI, milk yield (MY) at each milking, and vaginal temperature (VT, every 5 min) were recorded. Relative to CL, VT of NC cows had similar peak at 3 h, but remained greater before and after ivLPS (E � Time [T]: P < 0.01). ivLPS reduced DMI and MY (T: P < 0.01), without TRT � T interactions (P > 0.1). Typical ivLPS acute responses on peak concentrations of COR, PRL, TNFα and IL10 were respectively observed at 3, 1, 1, and 1 h after ivLPS (T: P < 0.01). CL-OG cows had greatest COR area under the curve (AUC) from 0 to 3 h (D � E, P = 0.07) than other TRT. Although CL-OG cows had greatest (P = 0.02) cortisol 1h after ivLPS, NC-OG reached similar peak as CL-OG at 3 h, which was greater (P = 0.03) than both CON TRT (D � E � T, P = 0.01). For CON cows, PRL AUC from 0 to 3 and 0—6 h were lower in NC cows; whereas both OG TRT had similar AUC, which did not differ from both CON TRT (D � E, P ≤ 0.04). OG cows tended to have greater (P = 0.09) IL10 AUC from 0 to 3 h than CON. In conclusion, OG increased acute hormonal response to ivLPS in NC cows (greater COR, intermediate PRL), and enhanced IL10 secretion regardless of E, suggesting OG enhances acute response to ivLPS while promoting a faster resolution.

Keywords: heat stress, OmniGen, inflammation.