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Effects of rumen protected choline supplementation during electric heat blanket induced heat stress.

H. T. Holdorf




Effects of rumen protected choline supplementation during electric heat blanket induced heat stress.
H. T. Holdorf*1, K. A. Estes2, B. A. Barton2, H. M. White1. 1University of Wisconsin-Madison Madison, WI, 2Balchem Corporation New Hampton, NY.

The negative impacts of heat stress (HS) on health and production are partially explained by reduced dry matter intake (DMI) and the immune response (IR) to lipopolysaccharide (LPS). The objective of this study was to determine if supplementation of rumen protected (RP) choline would ameliorate the negative impacts of HS using an electric heat blanket HS model that included a 3-d baseline and 7 d of HS. Multiparous Holstein cows were blocked by milk production, and randomly assigned to a control diet (CTL, n = 7), or CTL top-dressed with RP choline (60 g; ReaShure, Balchem Corp., New Hampton, NY) during the baseline and HS (RPC+, n = 8) periods or only during the HS (RPC, n = 8) period. Daily DMI and milk production were measured, and milk components were measured by sampling the last 4 milkings of each period. Blood samples were collected from the tail vessels and BW was measured on d1 and d11. Data were analyzed using the MIXED procedure of SAS 9.4. Preplanned contrasts (PPC) were CTL vs RPC, CTL vs RPC+, CTL vs both, and RPC vs RPC+. Percent change ((d11 - d1) / d1) of BW and blood metabolites were compared with 0% change by t-test. Means were considered significantly different if P ≤ 0.05, and a tendency if 0.05 < P ≤ 0.1. RP choline increased milk fat (PPC: P = 0.05) and tended to increase energy-corrected milk (ECM; PPC: P = 0.08) yields during HS. HS increased serum triglyceride concentration (+45.36%; t-test: P = 0.02) in CTL cows. HS decreased tumor necrosis factor α and alanine aminotransferase concentrations (t-test: P ≤ 0.01) in all cows. The effect of HS on LPS binding protein (LBP) concentration differed (PPC: P = 0.03) when comparing CTL (+24%) vs RPC (+1%) and RPC+ (−17%). RP choline was able to partially mitigate the effect of HS on ECM, with no evidence for increased DMI, suggesting altered nutrient use for energy output in milk. RP choline may have modulated the IR to HS, evidenced by the differential change in LBP. The mechanism by which RP choline influences the HS induced IR should be further explored as a potential nutritional strategy to mitigate negative impacts of HS on health and production.

Keywords: Heat abatement, immune response.

Biography: Henry Holdorf is a PhD student in Ruminant Nutrition at the University of Wisconsin-Madison in Dr. Heather White's laboratory and is a Ph.D. fellow with Purina Animal Nutrition.�Henry's research aims focus on aspects of nutritional physiology, especially as they relate to physiological challenges including negative energy balance, and thermal stress.