Abstract

Postpartum dairy cows fed more rapidly fermentable starch sources have depressed dry matter intake (DMI), compounding the risk of negative energy balance and hepatic lipid accumulation. Rumen-protected choline (RPC) is supplemented to periparturient dairy cows to facilitate hepatic lipid export. Our objective was to evaluate the interaction of dietary starch fermentability (DF) and RPC supplementation on postpartum DMI and performance. Prepartum supplementation of a low dose of RPC (no RPC [C−] vs. RPC [C+; 30 g/d]) began 21 d before the expected calving date for Holstein cows with at least one parity. Postpartum, cows were assigned to 1 of 4 postpartum treatments for 21 d with a 2 × 2 factorial arrangement of starch fermentability rate (low [dry-rolled corn; LFERM] vs. high [dry-rolled wheat; HFERM]) and RPC (C− vs. C+). Prepartum, C+ decreased DMI by 2.3 kg compared with C−, but there was no evidence of treatment effect on DMI postpartum. Time and DF interacted on milk yield, with HFERM increasing milk yield after d 3 compared with LFERM. Compared with LFERM, HFERM decreased milk fat content but not fat yield. For blood metabolites, C+ decreased plasma beta-hydroxybutyrate by 0.3 mmol/L and tended to increase glucose concentration compared to C−. In conclusion, supplementation with RPC at a low rate of inclusion reduced DMI in prepartum cows and decreased postpartum plasma BHB concentrations. Further work is required to elucidate potential mechanisms of action for RPC-mediated reductions in DMI.

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