Testing of trichomoniasis vaccine in heifers mated to infected bulls

This study was conducted to evaluate the effectiveness of a Trichomonas fetus vaccine to protect heifers from infection when bred to infected bulls. The vaccine consisted of a whole cell vaccine of T. fetus organisms stabilized in formaldehyde and adjuvanted in a mineral oil base. In the trial, fewer vaccinated heifers became infected than unvaccinated controls (69.4 vs 93.0%, respectively; P<0.08). The vaccinated heifers tended to clear the infections sooner than the controls (48.9 vs 68.5 days, respectively; P<0.10). The average number of days open was shorter in the vaccinated heifers than in the controls (33.2 vs 56.9 days, respectively; P<0.07). The first service conception rate was higher in the vaccinated heifers than in the controls (66.7 vs 33.3%, respectively; P<0.05). The number of services per conception in conceiving heifers was lower in vaccinated than in control heifers (1.44 vs 1.73, respectively; P<0.16). Cervicovaginal mucus (CVM) samples were collected every 14 days following first challenge (first service). On average, more CVM samples were positive for T. fetus for a longer period of time in the control than in the vaccinated heifers (3.9 vs 1.85 sampling periods, respectively; P<0.08). We concluded that, under the conditions of this trial, some protection to T. fetus was afforded by double vaccination with a whole cell vaccine. However, vaccination does not completely prevent heifers from developing infection.