Effects of vaccination with a Moraxella bovis bacterin on the subsequent development of signs of corneal disease and infection with M bovis in calves under natural environmental conditions.

A vaccination study was conducted for infectious bovine keratoconjunctivitis (IBK) in 440 purebred Hereford cattle (cows and their newborn calves) of the USDA Meat Animal Research Center cattle herd at Clay Center, Ne. The cattle were allotted to 4 groups: 60 calves were vaccinated with an autogenous Moraxella bovis bacterin (group 1); 60 calves that were matched with group 1 calves were designated nonvaccinated matched controls (group 2); 99 calves were peer group nonvaccinated controls (group 3); and 219 cows, the dams of the calves, were nonvaccinated consorts (group 4). The infection rates in cattle groups 1, 2, 3, and 4 during the summer were 96.6, 98.3, 100, and 79.1%, respectively, and the disease rates were 90, 93, 85, and 20%. The infection and the disease rates were significantly (P less than 0.01) different between claves and cows. The disease rate was also significantly different between older and younger cows. A larger percentage of the affected calves and cows had mild or moderate (61%) signs of IBK rather than severe (39%) signs. The rate of body weight gain was reduced in calves with severe signs of IBK. The results seemed to indicate that little would be gained by vaccinating cattle against IBK under the conditions of study.