Risk factors for subclinical endometritis and its effect on reproductive performance in small-scale dairy farms

The study aimed to evaluate the effect of subclinical endometritis (SCE) on reproductive performance and identify risk factors for this pathology in small-scale dairies. In four small-scale dairies, 608 lactations were monitored for health issues, nutritional status, and reproductive events, and SCE was diagnosed based on endometrial polymorphonuclear counting (PMN%) at 30±5 (SCE30) and 60±5 (SCE60) days postpartum. The threshold for diagnosis was established according to the quartile distribution of PMN%; 4 % and 2 % for SCE30 and SCE60. Conception rate at first service (CRFS), number of services per conception (SC), and days open (DO) were analyzed for SCE effect through Chi-square or ANOVA. Events of interest were considered in each lactation to perform a risk factor analysis using univariate logistic regression and multiple logistic regression model building. The population attributable fraction was calculated to identify the most important risk factors. Considering both sampling periods, 40.5 % of the cows were positive for SCE. SCE30-positive cows had lower CRFS (38.9 vs 53.7 %), required 0.4 more SC, and had 20.2 more DO than SCE30-negative cows (P ≤ 0.001). SCE60-positive cows had 16 more DO than SCE60-negative cows (P ≤ 0.01). The most important risk factors for SCE30 were retained fetal membranes (RFM) and uterine diseases, while calving season, RFM, and SCE30 status were the risk factors for SCE60. SCE could represent a major problem in small-scale dairies due to its prevalence and negative effect on reproductive performance. Furthermore, there are identifiable risk factors for SCE under these production conditions, which should be considered when designing prevention strategies.