CONICET | Buscador de Institutos y Recursos Humanos

During the periparturient period, dairy cows experience an increase in the prevalence of metabolic and production-related diseases. These health problems not only cause reductions in milk production and increases in production costs but also reduce the reproductive performance of cows. This study aimed to estimate the relative contribution of factors affecting the likelihood of pregnancy at the first service. We analyzed 66,935 lactations from 20 Argentinian dairies as function of two factors: parity season (warm: vs cool) and occurrence of early postpartum diseases (retained placenta 35%, hypocalcemia 3%, displacement of the abomasum 2%, metabolic diseases 36%, and mastitis 24%). Lactations were categorized according to the occurrence of diseases as follows: diseases appearing within 21 DIM, between 22 and 42 DIM, and without any disease. A logistic regression model was adjusted in JMP (v14.2) including parity, season, occurrence of postpartum diseases and their interaction independently for primiparous and multiparous cows. Parity and season affected the pregnancy odd ratio (OR) (P < 0.0001) while their interaction was not significant. Primiparous and multiparous cows without postpartum disease were 1.19 (OR, 95% CI: 1.13-1.26) and 1.23 (OR, 95% CI: 1.17-1.29) times more likely to conceive at the first service than those with a disease event during the first 21 days in lactation, respectively. The odds of pregnancy at first service were not affected by the occurrence of disease between 22 and 42 DIM. Primiparous and multiparous cows that calved during the cool season were 1.68 (OR, 95% CI: 1.59-1.77) and 1.61 (OR, 95% CI: 1.53-1.69) times more likely to become pregnant at first service than those who started in the warm season, respectively. We concluded that in addition to parity season, the occurrence of health events during the first 21 days postpartum impacts the reproductive efficiency at the first service of dairy herds.