Validation of different vaccination protocols against bovine respiratory disease in high-risk calves vaccinated after arrival on Swiss veal farms

INTRODUCTION: The objective of the study was to evaluate the efficacy of different vaccination protocols against bovine respiratory disease (BRD) for calves newly arrived at veal farms. Four farms in Switzerland were enrolled under field conditions each with three fattening periods. Commercially available vaccines were administered against bovine respiratory syncytial virus (BRSV), bovine parainfluenza virus type 3 and, partly, Mannheimia haemolytica. The calves (n = 418) were vaccinated on the day of arrival on the farms with either a live vaccine (LV), a killed vaccine (KV) or a placebo (P). After 21 days, a booster vaccine was administered in a reduced crossover design resulting in five vaccination protocols: LV/LV (n = 83), LV/KV (n = 82), KV/LV (n = 84), KV/KV (n = 80) and P/P (n = 89). Blood samples were collected from 223 calves on the day of arrival (day 1), day 3, day 21 and day 28 to assess BRSV antibodies and haptoglobin. Oral and parenteral antibiotic treatments were assessed as well as performance data, in particular daily weight gain. The seroprevalence of BRSV at time of arrival was high (86 %). Results revealed neither significant differences in respect to number of antibiotic treatments nor in the performance data for any of the applied vaccinations protocols. It is concluded that, considering the frame conditions, any vaccination of calves on arrival on the veal farm seems to be at an inappropriate point of time, i. e. an effective subsequent protection against BRD cannot be achieved in this way.