Colostrum from cattle immunized with a vaccine based on iron regulated proteins of Mannheimia haemolytica confers partial protection.

Passive protection afforded by colostrum from cattle vaccinated prepartum with an inactivated combination vaccine against viral pathogens and Mannheimia haemolytica (M. haemolytica) was evaluated against an experimental M. haemolytica challenge. Newborn calves were either fed colostrum from vaccinated dams or control colostrum. At approximately 3 weeks of age 24 calves were experimentally infected with M. haemolytica. Animals of both groups displayed clinical signs of respiratory disease and lung damage. The survival rate was considerably higher in calves which received colostrum from vaccinated cows. Colonies consistent with M. haemolytica were recovered in large numbers from all animals, but the geometric mean recovery was more than ten-times lower in the vaccinate colostrum fed animals. It can be concluded that maternal antibodies partly protected the calves against a severe M. haemolytica challenge.