Some effects of experimental Vibrio fetus (venerealis) infection on cattle inoculated with a commercial bacterin.

Four groups of ten heifers were used to study the effect of a commercial Vibrio fetus bacterin on the development of vaginal mucus agglutination (VMA) reactions and subsequent reproductive performance in the presence of active V. fetus infection. Two groups were vaccinated and one of these was infected one month later. The other two groups were not vaccinated and one of these was infected. It was found that in the absence of infection the bacterin did not produce diagnostically significant VMA reactions but in the presence of infection reactions comparable with the control group were detected. The infected control group required 4.9 services per conception, the first service-conception interval was 126.9 days and 50 per cent of the animals aborted. The corresponding figures in the infected vaccinates were 3.5 services, 68.9 days and 12.5 per cent abortions. It was concluded that although this bacterin has a beneficial effect on reproductive performance in the presence of genital vibrosis, maximum breeding efficiency will not be obtained unless V. fetus infection is eliminated. Persistent local reactions appeared at the site of inoculation in the majority of the vaccinated animals.