Field trial of the effect of vaccination against Bovine herpesvirus 1 on milk yield and rumination time: comparison between two live marker vaccines
In a dairy farm using a voluntary milking system (VMS), two homogeneous groups of dairy cows were formed. For each group the VMS automatically determined daily data related to individual milk yield (MY) and rumination time (RT). Data were analyzed from 3 days before vaccination to 6 days after vaccination, which was performed with 2 live attenuated IBR marker vaccines regularly marketed in Italy (group A: BioBos IBR marker live and group B: Bovilis IBR marker live). Data from groups A and B were statistically compared to determine differences within the group before and after vaccination, as well as differences between the groups. The between group analysis failed to find a difference in MY, but A had higher RT than B the first day after vaccination (P<0.05). In group A, vaccination had no effect on both MY and RT, conversely, in group B, MY did not change after vaccination and RT decreased on the day after vaccination, but returned to pre-vaccination values on day there. Rumination time is known to be one of the indicators of animal welfare, i.e., absence of stressors. This study showed that vaccination against IBR with the selected products had no effect on milk yield and had a very little effect on RT limited to the first day after vaccination. The latter is mainly due to reduction of RT in group B and indicated a slightly altered physiological homeostasis, whereas group A maintained the same rumination behavior as before vaccination.