An intervention study to compare the outcome of administering a live intranasal Bovine Respiratory Syncytial Virus and Parainfluenza-3 vaccine to maternally derived antibody positive calves on the day of birth with calves vaccinated at one week of age.

The aim of the study was to demonstrate the efficacy of Bovilis INtranasal RSP Live administered on the day of birth (DoB) compared with administering the same vaccine between seven and ten days of age (D7). Health (including antibiotic treatments), mortality outcomes and weights in two groups of calves (DoB and D7) were monitored. Calves (n = 847) from seven farms were administered the vaccine on DoB or between day 7 and day 10 (D7) of life. Animals were weighed at week 1, weeks 3-4 and week 8 of life, using weigh tapes. Average daily liveweight gains (DLWG) were calculated. Adverse health events, treatments and mortality were recorded by farmers. Overall mean growth rate was 0.64 kg/day in the first eight weeks of life, with high intra-farm variability in DLWG (0.31-0.81 kg/day). Mixed linear and Poisson models (with farm as a random effect) revealed no statistically significant effect of vaccination timing on any of the outcomes of interest. Animals were kept in the same environment, such that cross-protection from vaccination in the DoB group could have decreased the true effect size of differing vaccination protocols. Results suggest that Bovilis INtranasal vaccination may be administered on DoB or D7 equivalently, depending on respiratory disease risk and farmer and veterinarian preference.