Risk factors for post-calving intramammary infection with Mycoplasma spp. in first lactation cows on a conventional dairy farm: A retrospective case control study.

Mycoplasma spp.are highly contagious bacteria that cause chronic, subclinical infections in dairy cattle and are intrinsically resistant to many antimicrobials.This retrospective cohort study evaluated whether different calfhood and peripartum variables were associated with post-calving intramammary Mycoplasma spp.infections.We analyzed data from 475 first-lactation animals from one commercial dairy herd, comprising 95 cases with intramammary infections caused by Mycoplasma spp.and 380 culture-negative controls.Data on colostrum Brix%, birth body weight, otitis and pneumonia events, age at first breeding, age at conception, days in the close-up pen, age at calving, days in the fresh cow pen, and calving season were retrospectively extracted from electronic herd records and analyzed using univariable logistic regression models.We found that age at the first otitis event was associated with the occurrence of an intramammary infection with Mycoplasma spp.Cows that experienced an otitis event during calfhood, specifically at 23 d of age, had greater odds of post-calving intramammary infection with Mycoplasma spp.No associations were found for other variables.These results suggest that otitis in early life may represent an important predictor of susceptibility to intramammary Mycoplasma spp.infection post-calving and highlight the potential value of calfhood monitoring for mastitis prevention strategies.