Effect of bovine viral diarrhea virus on conception in cattle.

Sixty adult dairy cows were used to study the effect of bovine viral diarrhea (BVD) virus on conception when inoculated with the virus within 2 hours after breeding. Fifteen cows were assigned at random to each of 4 groups. Group I (control) cows were given 3 ml of diluent in the uterus; group II (seropositive) cows were given 3 ml of BVD virus in the uterus; group III (seronegative) cows were given 3 ml of BVD virus in the uterus; and group IV (seronegative) cows were given 3 ml of BVD virus orally and 3 ml intranasally. At 35 days after breeding, the cows were slaughtered, their reproductive tracts were recovered, and pregnancy rates were recorded. The pregnancy rates for groups I, II, III, and IV were 67%, 60%, 27%, and 67%, respectively. The group III pregnancy rate was significantly lower (P less than 0.05) than that for the control group. However, the similarity of rates for groups I, II, and IV indicates that BVD virus does not inhibit conception when cattle are infected by natural routes or when virus is infused into the uterus of seropositive cows at the time of breeding. These results indicate that BVD virus is not a major cause of repeat breedings in cattle.