Effects of vaccination against 18 immunogens in beef replacement heifers at weaning

Humoral immune responses to vaccination, mean daily body-weight gains, morbidity, and mortality were compared in groups of beef replacement heifers from weaning to 4 months after weaning. The only difference in management among groups of heifers was the number and type of vaccines they received. Heifers were vaccinated at weaning (mean age, 205 days) and again 28 days later against 0, 1, 9, 10, 17, or 18 antigens, using commercially available monovalent and multivalent vaccines. The common vaccine component in all treatment groups was a modified-live bovine respiratory syncytial virus. Mean daily gain, morbidity, mortality, and serum neutralization antibody titers to bovine respiratory syncytial virus did not differ among treatment groups. Although the study revealed the safety of vaccinating beef heifers against 18 antigens at weaning, our data emphasized the need for serial vaccination to induce a measurable serum antibody response.