Bovine pestivirus infection: a cause of ovulatory disturbance in dairy cows

Twelve (Experiment I) and four (Experiment II) multiparous dairy cows seronegative to pestivirus were selected and randomly assigned to either a control group which did not become infected or a treatment group in which all cows became infected following intranasal inoculation 9 days before AI. The experimental induction of infection was carried out with 2 ml of non-cytopathic pestivirus (BVD virus) suspension containing 5 log10 TCID50/ml (Experiment I) and 4.5 log10 TCID50/ml (Experiment II). In both experiments, the cows were superovulated on day 10،ہ2 of the cycle using the standard procedures. The cows in Experiment I were artificially inseminated at 12 and 24 h after the onset of estrus and a non-surgical ova/embryo collection was performed 7 days after AI. In Experiment II, the cows were slaughtered on day 8 after superovulation-induced estrus and the ovaries submitted for gross and histopahological examination including immunohistochemistry. Mean (،ہSE) number of ovulatory sized follicles on day of AI and corpora lutea palpated on day 7 after AI were significantly (p0.05) higher in control un-infected cows compared to that of the pestivirus infected cows (17.1،ہ2.6 vs. 9.2،ہ1.1 and 12.2،ہ2.7 vs. 2.8،ہ0.9), respectively. On histopathological examinations, the mean (،ہSE) number of unovulated lutenised follicles (،ف 9mm in diameter) present on the ovaries of the control cows on day 8 after estrus was 6.8،ہ4.9 compared to 12.5،ہ5.4 for the infected cows. Further, many corpora lutea in the ovaries of infected cows had a hypoplastic or atrophic wall. In conclusion, the present study demonstrated that pestivirus infection during the period of final growth of preovulatory follicles results in a disturbance in ovulation and development of corpus luteum leading to a poor superovulatory response in multiparous dairy cows.