Non-Specific Effects of Prepartum Vaccination on Uterine Health and Fertility: A Retrospective Study on Periparturient Dairy Cows

Prepartum vaccination of dairy cows against newborn calf diarrhea protects calves during the first weeks of life via the colostrum. Vaccination may also induce non-specific effects (NSE) beyond antibody production, altering disease susceptibility and productivity of the vaccinated mother. This retrospective study analyzed herd records and on-site survey data from 73,378 dairy cows on 20 German farms using linear mixed-effects models and random forest algorithms. Management practices and milk yield showed stronger associations with outcomes than vaccination. However, cows vaccinated with non-live vaccines had increased odds of retained placenta and metritis (OR: 1.5–1.7), and endometritis (OR: 3–6), and were 20–24% less likely to be successfully inseminated than non-vaccinated cows. Among non-live vaccinated cows, those vaccinated 2.5–4 weeks before calving had an 8% higher non-return rate compared to those vaccinated 6–8 weeks prior. Multiparous cows receiving live vaccine components were 1.9 times more likely to be successfully inseminated, compared to non-live vaccinated multiparous cows. These findings suggest poten-tial NSE of prepartum vaccination on uterine health and fertility. However, the study’s retro-spective design limits causal interpretation, and the benefits in calves may outweigh possible adverse effects. Further research should clarify mechanisms and optimize vaccine timing and composition.