THE EFFECT OF BOVINE PESTIVIRUS INFECTION ON THE SUPEROVULATORY RESPONSE OF FRIESIAN HEIFERS

The pathogenesis of reproductive loss associated with bovine pestiviru s infection during the preovulatory period was investigated using supe rovulated heifers. Twenty-five Friesian heifers were selected and rand omly assigned to either a control group (n=12) which did not become in fected or to a treatment group (n=13) which became infected following intranasal instillation of 2 ml of serum inoculum containing 5.5 log(1 0) TCID50/ml non-cytopathic virus, 9 d prior to artificial inseminatio n (Al). Transrectal ultrasonography was used to monitor follicular dev elopment and ovulation during the superovulatory period. Animals were superovulated using a standard protocol of twice-daily injections of F SH-P and then were inseminated twice commencing 12 h after the onset o f estrus. The intensity of expression of estrus was higher in the cont rol heifers than in the pestivirus-infected heifers. Of 13 pestivirus- infected heifers, only 3 heifers displayed standing estrus compared wi th that in the control group, in which 10 of 12 heifers exhibited stan ding estrus. The mean number of ova/embryos recovered from the control group heifers was 5.75 +/- 2.31, of which 4.00 +/- 0.72 were evaluate d as transferable quality embryos. In comparison, heifers in the pesti virus-infected group yielded only a mean of 0.60 +/- 0.34 ova/embryos, of which 0.23 +/- 0.22 were transferable quality embryos. Based on ul trasonographic examination, 24 h after the first Al 82% of the presump tive ovulatory follicles had ovulated in the control group compared wi th an ovulation rate of only 17% in the treated group. The results of this experiment demonstrated that bovine pestivirus infection during t he preovulatory period could adversely affect ovulation, thus leading to a significant reduction in the number of palpable corpora lutea and in the number and quality of embryos recovered. (C) 1997 by Elsevier Science Inc.