The efficacy of trypsin for disinfection of in vitro fertilized bovine embryos exposed to bovine herpesvirus 1

Bovine cumulus—oocyte complexes (COC) or in vitro fertilized (IVF) embryos were exposed to bovine herpesvirus 1 (BHV-1) during in vitro maturation or co-culture with uterine tubal cells, respectively. Trypsin, at a concentration of 0.25%, was applied (for approximately 90 s) to disinfect either COC or cumulus-free oocytes (CFO) 18 h after insemination, or on day 7 to embryos resulting from infected oocytes. In total, virus was not detected in 71% of 93 samples containing 233 embryos exposed to BHV-1 and trypsin treatment. BHV-1 was detected in 14% and 54% of samples containing a single embryo and five embryos, respectively. In corresponding groups of embryos exposed to BHV-1, then washed but not treated with trypsin (70 samples), 85% and 96% of samples containing one embryo and pooled embryos, respectively, were positive for the virus. There was no effect of trypsin treatment on the development of IVF-embryos. It is concluded that IVF-generated embryos have a greater tendency to carry BHV-1 after experimental exposure to the virus than IVF uterine stage embryos, and that they are more difficult to disinfect by means of the standard trypsin treatment use.