Effect of vaccination against bovine herpesvirus 1 with inactivated gE-negative marker vaccines on the health of dairy cattle herds

The aim of this study was to estimate the effect of the bovine herpesvirus 1 (BHV-1) vaccination on herd health and production in BHV-1 infected Estonian dairy cattle herds. Seven herds vaccinated with inactivated gE-negative BHV-1 marker vaccines and seven matched non-vaccinated herds were selected. In vaccinated herds the calving interval was on average 7.01 days shorter compared to that in the non-vaccinated herds (coef = −7.01, 95% CI = −11.98, −2.03, p = 0.008) during the study period (2007–2012). In non-vaccinated herds the insemination index had an increasing trend (coef(log scale) = 0.03, 95% CI = −0.003, 0.06, p = 0.054) and the first service conception rate decreased (coef = −2.19, 95% CI = −3.91, −0.47, p = 0.015), whereas no significant changes occurred in vaccinated herds. Average yearly milk yield per cow increased (coef = 145.30, 95% CI = −6.11, 296.71, p = 0.065) and length of the dry period decreased in BHV-1 vaccinated herds (coef(log scale) = −0.02, 95% CI = −0.04, 0.004, p = 0.056) compared to non-vaccinated herds during the study years. Youngstock and the cow culling rate due to respiratory disease was significantly lower in vaccinated herds compared to non-vaccinated herds (coef = −0.29, 95% CI = −0.47, −0.11, p = 0.003 and coef = −0.15, 95% CI = −0.29, −0.007, p = 0.043, respectively). These results suggest that vaccination against BHV-1 is associated with herd health and productivity.