Prepartal vaccination has no influence on mammary health and milk yield of dairy cows: a retrospective study addressing non-specific effects of vaccination

Abstract Background: Prepartal vaccinations against newborn calf diarrhea pathogens are performed in the last weeks of pregnancy, with the intention to induce a maternal adaptive humoral immune response and to protect calves in the first weeks of life via colostral transferred pathogen-specific antibodies. There is evidence that vaccination-related innate immune responses can also affect the mother's immune system response to stressors. Whether such non-specific vaccine effects alter the disease susceptibility of dairy cows in the very sensitive transition period has not been addressed so far. In a retrospective cross-sectional study, we investigated the influence of prepartal maternal vaccination on mammary health and milk yield of the periparturient dairy cow. Herd record data from 73,378 dairy cows from 20 farms located in Eastern Germany, together with on-site-collected survey data, were analyzed using linear mixed-effects regression, quantile regression and random forest machine-learning algorithms. A total of 57,166 transition periods without prior vaccination, distributed along 16 herds, and 63,228 transition periods on 13 herds with prior vaccination are included. Additionally healthy primiparous cows from alternately vaccinated herds were analyzed. Results: Herd management-related factors, such as herd in general and calving year, as well as parity proved to be most influential for mammary health and milk yield, while prepartal vaccination occurred as least influential. Vaccinated cows did not show significant differences in mastitis prevalence and somatic cell count as compared with non-vaccinated cows. Also, energy corrected milk yield on first test day of milk recordings, as well as in 305-days of lactation, of healthy primiparous cows with and without prior vaccination showed no significant differences. Conclusions: This study presents evidence that prepartal vaccination against newborn calf diarrhea does not have significant non-specific effects on mammary health and milk yield parameters. Instead, the findings highlight the importance of herd management factors. This work emphasizes the significance of multivariable analysis based on a large database with high statistical power. It also recommends further research to explore potential non-specific vaccination effects on other organ systems, infectious diseases, and production metrics in cows.