Reduction in daily milk yield associated with sub-clinical bovine herpes virus 1 infection

The aim of this observational cohort study was to investigate the potential economic effect of sub-clinical Bovine Herpes Virus 1 (BoHV-1) infection in a commercial UK dairy herd in terms of milk yield depression. Infection status of cows (infected or not infected) was assigned from serology on a single occasion. A multi-level linear model was used to evaluate the effect of infection status on milk production, using milk records that were routinely collected over two years. BoHV-1 seropositive cows produced 2.6 kg/day less milk over the study period compared with cows that were seronegative. This result highlights the importance of appropriate management of risks associated with BoHV-1 as part of proactive herd health and production management