Abstract
INTRODUCTION: Early vaccination of cattle with an inactivated commercial bacterial vaccine against bovine respiratory disease has been reported to increase antibody production and can alleviate the disease. However, its dosage has been little investigated in young Holstein calves. This study addresses the need to establish guide values for vaccine dosage in these animals. MATERIAL AND METHODS: Healthy calves received an inactivated vaccine for Histophilus somni, Pasteurella multocida and Mannheimia haemolytica intramuscularly at the ages of 1 and 4 weeks. Administered vaccine doses were 1.0 mL for the primary and booster vaccinations (1.0 + 1.0 group), 0.5 mL for the primary and 1.0 mL for the booster vaccination (0.5 + 1.0 group), or 0.5 mL for both vaccinations (0.5 + 0.5 group). RESULTS: Differences in the vaccine responses between the 1.0 + 1.0 group and 0.5 + 1.0 group were minor. However, the number of calves with a positive vaccine response to H. somni in the 0.5 + 0.5 group was less than half of that in the 1.0 + 1.0 and 0.5 + 1.0 groups. In logistic regression analysis, although the booster vaccination dose was positively correlated with seropositivity for H. somni, the primary vaccination dose was not correlated with vaccine response. The number of calves with positive vaccine responses to M. haemolytica was low even after booster vaccination regardless of the dose. CONCLUSION: The dose of 0.5 mL can be used for primary vaccinations in newborn Holstein calves, but 1.0 mL may be required for booster vaccinations.