A randomized control trial investigating the effectiveness of a commercial pneumonia vaccine (part I): Pre-weaned lambs

The objective of this controlled vaccine field trial was to determine the effectiveness of a commercial bacterin in increasing colostral immunity to reduce the risk of bacterial pneumonia in pre-weaned lambs in a commercial sheep operation. Pregnant ewes were randomly allocated to vaccination group (Ovipast™ Plus bacterin, n = 1807; unvaccinated, n = 1812). Ewe vaccination did not significantly (P > 0.05) improve lamb pneumonia treatment rates, crude or pneumonia specific mortality rates, or body weight gain. Interestingly, as birth weight increased in lambs from vaccinated ewes, they gained significantly more than lambs from unvaccinated ewes (P = 0.01). There was no difference in culture results from pneumonic lung samples for either Mannheimia haemolytica (P = 0.89) or Bibersteinia trehalosi (P = 1.00) between lambs from vaccinated and unvaccinated ewes. The results of this study suggest that there was no animal health and welfare benefit from vaccinating ewes with the Ovipast™ Plus bacterin prior to parturition to boost colostral immunity and improve health and growth in their lambs.