Immunization of calves against salmonellosis.

Fifty-six normal colostrum-fed Holstein-Friesian and Holstein-Friesian X Angus crossbred calves ranging in age from 3 to 9 weeks were divided into 4 vaccinated groups and 1 nonvaccinated (control) group. Group I consisted of 10 calves vaccinated 2 or 3 times subcutaneously with formalin-killed Salmonella dublin-S typhimurium bacterin with added adjuvant. Group II consisted of 4 calves vaccinated orally with formalin-killed S typhimurium daily for 21 days. Group III consisted of 17 calves given colostrum from dams which had been vaccinated twice subcutaneously with a formalin-killed S dublin-S typhimurium bacterin with added adjuvant. Group IV consisted of 8 calves orally given small doses of live virulent S typhimurium twice. Seventeen calves served as nonvaccinated controls. One to 2 weeks after the final vaccine dose (or at 3-weeks of age for group III), all calves were orally challenge exposed with virulent S typhimurium. Oral challenge dose levels ranged from 1.5 X 10(9) viable organisms to 1.5 X 10(11) viable organisms. Mortality following oral challenge exposure was 11 of 17 controls, 6 of 10 group I calves (ns), 2 of 4 group II calves (ns), 11 of 17 group III calves (ns), and 1 of 8 group IV calves (p = 0.001). Twenty calves, 4 from group I, 8 from group III, and 8 from the control group, given 1.5 X 10(11) challenge organisms (the largest challenge, inoculum) died, whereas only 1 of 6 calves in group IV given this dose died. Group II calves were not given the 1.5 X 10(11) challenge dose. Under the conditions of this experiment, bacterins given parenterally or orally to calves or given parenterally to the dams of calves did not decrease morbidity and mortality, whereas small numbers of live organisms given orally to calves were effective in lessening morbidity and mortality following oral challenge exposure with virulent S typhimurium.