Influence of Bovine Viral Diarrhea Virus Infection on Artificial Insemination Conception and Breeding Season Pregnancy Success in Vaccinated Beef Herds

Abstract

Bovine Viral Diarrhea Virus (BVDV) causes reproductive economic losses in cattle. The objective of this study was to evaluate the influence of BVDV infection on reproductive success. Vaccinated cows (n = 370) and heifers (n = 528) from nine different herds were synchronized using the 7-day CO-Synch + CIDR protocol and were bred using fixed-time artificial insemination (FTAI). On d 28 following insemination, blood samples were collected and pregnancy status was determined. Non-pregnant animals were resynchronized and FTAI occurred a second time. In six herds, bulls were comingled with females beginning 10-15 d after the second AI. Final pregnancy status was determined 33-80 d following the first pregnancy diagnosis. Blood samples were tested for the presence of BVDV antigen using the IDEXX BVDV PI X2 Kit. Animals that tested positive were considered infected with BVDV at the time of blood collection. Herds were determined to be BVDV infected by the presence of at least one animal having a positive test for antigen (n = 4 infected herds, n = 5 non-infected herds). Statistical analyses were performed using the GLIMMIX procedure of SAS with herd as a random variable. Herds that had evidence of BVDV infection at d 28 following insemination had significantly decreased (P \u3c 0.01) first service AI conception rates compared to herds that had no evidence of infection (34 ± 2.3% vs. 54 ± 2.3%, respectively). Additionally, breeding season pregnancy rates were decreased (P \u3c 0.01) in BVDV infected herds compared to non-infected herds (69 ± 3.4% vs. 80 ± 3.6%, respectively). There was no significant effect of BVDV infection status on embryonic loss (P = 0.42) or percentage of animals which lost a pregnancy and rebred by the end of the breeding season (P = 0.63). In conclusion, BVDV infection in well vaccinated herds had a significant negative impact on both first service AI conception rate and overall breeding season pregnancy success