The effect of natural and artificial breeding using bulls infected with, or semen contaminated with, infectious bovine rhinotracheitis virus.

Ten cows and heifers (Group B) were inoculated into the uterus at oestrus with semen followed by IBR virus for the first insemination and semen alone if a second insemination was necessary. All animals developed infectious pustular vulvo-vaginitis (IPV), and 2 cows conceived to the first and 2 to the second insemination (pregnancy rate of 40 percent requiring 4.5 services per conception). This group was compared with 10 control animals (Group A) which were treated similarly but received tissue culture fluid instead of virus at the first insemination. Group A had a pregnancy rate of 90 percent requiring 1.7 services per conception. Natural mating of 4 bulls with preputial infections due to infectious bovine rhinotracheitis (IBR) virus with 9 susceptible cows and heifers (group D), resulted in the production of lesions of IPV. The IPV infection did not affect their fertility (pregnancy rate of 89 percent requiring 1.4 services per conception) when it was compared to a similar group of females (group C) mated to the same bulls prior to infection with IBR virus (pregnancy rate of 100 percent requiring 1.2 services per conception). The 6 animals in Group B that were not pregnant and returned to oestrus 3 times were found on slaughter to have endometritis, salpingitis and vaginitis. A high incidence, 5 out of 18 (28 percent), of shortened oestrous cycles (less than 18 days) was a feature of the breeding pattern of this group. The undesirable consequences of distributing semen contaminated with IBR virus from artificial insemination centres are apparent.