DOUBLE-BLIND FIELD-EVALUATION OF A TRIVALENT VACCINE AGAINST RESPIRATORY-DISEASE IN VEAL CALVES

A field trial was performed to determine the effect of a trivalent vac cine on Clinical Respiratory Tract Problems (CRTP) in veal calves. The vaccine has been developed to increase immunity against the causal ag ents of IBR, BVD and BRSV infection. In total 928 calves, housed in 16 compartments of one herd, were involved. In four compartments of 58 c alves each, vaccinated and non-vaccinated calves were housed together. Four other compartments were treated as a whole and 8 compartments we re left untreated. CRTP incidence, medications, weight gain, haemoglob ulin and IgG level were recorded. From CRTP positive animals, seroconv ersion and presence of specific bacteriae and/or viruses were measured as well. Results of the compartments where vaccinated and nonvaccinat ed calves were housed together showed that the incidence of CRTP in va ccinated calves was 0.16 while it amounted to 0.28 in controls. Most c ases were found between day 40 and 60 after the start of the trial. Se roconversion for vaccine specific viruses was sporadically found, but the presence of Pasteurella's was confirmed in the majority of cases. Presumably, the higher incidence of CRTP in the control group was due to a higher level of BVDV infection which might facilitate a clinical infection with Pasteurella's. Vaccination was also negatively related to the percentage of affected lungs at slaughter, the number of days a ntibiotics had to be administered and subsequently to medicine costs, although these effects were not significant. Daily weight gain was sig nificantly affected by CRTP, but not by vaccination. The effects of va ccination in the compartments where calves were either all vaccinated or not-vaccinated, were similar or larger when compared to the effects in compartments where half of the calves were vaccinated.