Calves were immunised by the subcutaneous administration of 5 ml of an inac
tivated antigen preparation of Pasteurella haemolytica (3 x 10(9) cfu/ml).
After challenge, a significant difference was observed in the severity and
extent of pneumonic change between immunised and control animals. The admin
istration of sis intradermal inoculations of inactivated antigen and two ap
plications of OMP-antigens were of comparable efficacy.