Subclinical endometritis and its impact on reproductive performance in grazing dairy cattle in Argentina.

Recently several studies have reported that subclinical endometritis impairs reproductive performance in cattle. Most of the studies were conducted in western industrialized countries under intensive housing conditions. The objective of the present study was to determine the prevalence of subclinical endometritis and its impact on reproductive performance outcomes in clinically healthy postpartum dairy cows in a pasture-based extensive dairy farming system in Argentina. Lactating Holstein cows (n=201) at 18-38 days postpartum (dpp) from three commercial dairy farms in Buenos Aires Province, Argentina, were examined for signs of clinical endometritis by external inspection and manual vaginal examination. Only cows without signs of clinical endometritis i.e. no vaginal discharge were enrolled in this study and examined for subclinical endometritis using the cytobrush technique. Cows with ≥5% polymorphonuclear cells (PMN) in the cytological sample were regarded as affected by subclinical endometritis. All cows were reexamined 14 days later following the same examination protocol. Prevalence of subclinical endometritis 18-38dpp was 38% and decreased to 19% at reexamination. The proportion of cows pregnant at first service was 29% and proportion of cows pregnant at 360pp was 73% and 75% in cows with subclinical endometritis and those without, respectively. The probability of conception at first service, hazards of insemination and pregnancy, respectively, were not affected by subclinical endometritis. Primiparous cows had a greater chance for insemination (HR=0.66; 95% CI=0.47-0.92) and pregnancy (HR=0.63; 95% CI=0.45-0.90) than multiparous cows. In conclusion subclinical endometritis did not affect reproductive performance outcomes in a pasture-based, extensive dairy farming system in Argentina.