Abstract #W109

# W109
Effects of fully-acidified, negative DCAD diets with differing concentrations of dietary calcium fed prepartum on the dominant follicle of the first follicular wave after parturition and pregnancy in Holstein cows.
K. Ryan1, A. Guadagnin*1, K. Glosson1,2, S. Bascom2, A. Rowson2, F. Cardoso1, 1University of Illinois, Department of Animal Science, Urbana, IL, 2Phibro Animal Health Corporation, Teaneck, NJ.

Diets fed during the transition period can play an important role in the cow’s follicular dynamics following parturition. We aimed to compare the effects of feeding a fully-acidified, negative DCAD diet prepartum to multiparous Holstein cows (n = 70) at 2 concentrations of dietary calcium (Ca) inclusion versus a non-acidified, positive DCAD diet prepartum on follicular dynamics and pregnancy postpartum. Treatments began at 28d before expected calving and were: CON(n = 23), a positive DCAD diet with low dietary Ca (0.4% DM); LOW(n = 22), a fully-acidified, negative DCAD diet (urine pH = 5.7) with low dietary Ca (0.4% DM); and HIGH(n = 25), a fully-acidified, negative DCAD diet (urine pH = 5.7) with high dietary Ca (2.0% DM). Follicular development was monitored via ultrasound every 2 d starting at 7 DIM until ovulation of the first dominant follicle (DF). Data were analyzed using the MIXED, LIFETEST, and PHREG procedures in SAS. Association between treatments and days to first ovulation and pregnancy per first timed AI (P/AI) were assessed using Kaplan Meier curves and Cox’s proportional hazard regression. Contrasts included CONT1 (CON vs the average of LOW and HIGH) and CONT2 (LOW vs HIGH).Cows fed CON (18.95 ± 0.9 d) had increased (P = 0.01) days to first ovulation than cows fed LOW (17.13 ± 0.6 d) and HIGH (16.12 ± 0.4 d).There was no treatment effect on maximum DF diameter (CON = 17.87mm, LOW = 18.33mm, and HIGH = 17.56mm; SEM 0.44; P = 0.44, CONT1 and P = 0.16, CONT2).There was a tendency for a treatment × days relative to ovulation interaction (P = 0.11) indicating that cows fed CON had a slower rate of growth in the 4 d before ovulation of the first DF than cows fed LOW or HIGH. Cows fed CON (4/19 P/AI) tented to had lower P/AI (P = 0.11; 95CI = 1.02 – 16.6) than cows fed HIGH (11/21 P/AI) but not LOW (8/20 P/AI). In conclusion, cows fed HIGH and LOW had improved days to first ovulation than cows fed CON. Cows fed HIGH tended to be more likely to become pregnant than cows fed CON. Overall, cows fed a fully-acidified, negative DCAD diet prepartum had improved reproductive performance postpartum.

Key Words: dietary cation-anion difference (DCAD), follicle, pregnancy