Effects of induced parturition and estradiol on feed intake, liver triglyceride concentration, and plasma metabolites of transition dairy cows

The effect of induced parturition and estradiol on feed intake, liver trigl yceride, plasma metabolites, and milk yield was evaluated in fifty-six Hols tein cows and heifers. Cows were assigned to treatments on d 260 of gestati on and were on trial until d 10 postpartum for measurement of dry matter in take (DMI), plasma metabolites, and liver triglyceride and until d 31 postp artum to measure milk yield. Fourteen animals per group (9 cows and 5 heife rs) received either a placebo, 1 mg of fenprostalene, 50 mg of estradiol-17 beta benzoate, or both on d 276 of gestation. Cows that received fenprosta lene consumed more dry matter (DM) for the last 8 d prepartum than did cows that did not receive fenprostalene (9.6 kg/d vs. 8.5 kg/d, respectively) b ut consumed less DM for the first 10 d postpartum (10.9 kg/d vs. 13.1 kg/d, respectively). Cows injected with estradiol-17 beta benzoate tended to con sume less DM postpartum than did cows not injected with estradiol-17 beta b enzoate (11.3 kg/d vs. 12.7 kg/d, respectively). There was no effect of tre atment on milk yield; however, a fenprostalene by day interaction resulted fi om lower milk yield on d 3, 4, 5, 7, and 10 relative to calving in cows that received fenprostalene. Administration of fenprostalene resulted in a delay in the peak plasma nonesterifed fatty acid (NEFA) concentration until 2 d after calving. Plasma glucose concentrations were greatest 1 d prior t o calving for cows that received fenprostalene, whereas plasma glucose conc entrations peaked on the day of calving for cows that did not receive fenpr ostalene. Liver triglyceride increased over time; however, there was no eff ect of treatment on liver triglyceride. Calving induction improved DMI for the last 8 d prepartum, but a concomitant decrease in Liver triglyceride af ter calving did not result. Estradiol-17 beta benzoate had no effect on pla sma metabolites or liver triglyceride, indicating that the physiological ri se in estradiol prior to calving does not have a primary role in lipolysis or hepatic fatty acid metabolism in the dairy cow.