Abstract #108

# 108
Early genomic prediction of daughter pregnancy rate is associated with improved fertility outcomes in Holstein dairy cows.
F. S. Lima*1, F. T. Silvestre2, F. Penagaricano3, W. W. Thatcher3, 1Department of Veterinary Medicine, University of Illinois, Urbana, IL, 2Zoetis Inc, Kalamazoo, MI, 3Department of Animal Sciences, University of Florida, Gainesville, FL.

The use of genomic testing for selecting replacement heifers in commercial farms has recently attracted much attention. Genomic prediction of daughter pregnancy rate (GDPR) is one of the low heritability traits that have the potential to benefit the most from the genomic selection. Our objectives were to assess the relationships between GDPR and pregnancy for the first service (P1), pregnancy at the end of lactation (PEND), number of services for conception (NS), days from calving to first service (TP1), and days open (TPEND). Data for GDPR, reproductive parameters, and milk production (MP) from 1401 primiparous and 3044 multiparous Holstein cows, located in 4 farms with the same reproductive management, were used in the analyses. Data for GDPR and MP (first 2 mo for first service or 305 milk-equivalent for pregnancy at the end of lactation) were categorized in quartiles. Data were analyzed separately for primiparous and multiparous cows. Generalized linear models for P1, PEND, NS, TP1 and TPEND included the effects of GDPR, farm, MP, and the interaction between GDPR and MP. There were positive effects of GDPR (P < 0.01) in primiparous and multiparous cows for P1, PEND, NS, TP1, and TPEND. An effect of farm (P < 0.01) was detected for primiparous and multiparous for PEND, NS, TP1, and TPEND, and P1 in multiparous. An effect of MP was found (P < 0.01) for PEND in primiparous and multiparous, and NS for primiparous. Positive GDPR effects include a 22.5% higher P1 (55.5% vs. 33.0%), 15.3% higher PEND (80.9% vs. 65.6%), and 48.7 d shorter TPEND (129.3 vs. 178.0 d) for the highest GDPR quartile compared with the lowest GDPR quartile in multiparous cows. An interaction between GDPR and MP was detected for NS in primiparous cows only, where high-producing cows had fewer NS as GDPR increased, whereas no relationship between GDPR and NS was observed in low-producing cows. In summary, GDPR was a strong predictor for all reproductive parameters measured in both primiparous and multiparous cows, and interactions with milk production were restricted to NS in primiparous cows.

Key Words: genomic, daughter pregnancy rate, fertility