Prevalence of endometritis and its effects on reproductive performance of dairy cows

Hostein cows (n = 141) in five commercial dairy herds in central New York were examined for endometritis by examination of endometrial aspirates for presence of inflammatory cells, principally neutrophils, by endometrial cytology at 40–60 days postpartum. The prevalence of cytologically-diagnosed endometritis was 53%; within herds the prevalence varied from 37 to 74% (P = 0.02). There was excellent agreement between two examiners (Kappa = 0.864; P < 0.0001). Parity did not influence prevalence of endometritis (P = 0.53). Cytologically diagnosed endometritis was associated with profoundly impaired reproductive performance; Kaplan-Meier survival analysis revealed lower overall pregnancy rate (P < 0.0001). Median days open was 206 for cows with endometritis and 118 for cows free of the condition. Overall, 76% of cows in this study became pregnant by 300 days postpartum; 63% of cows with endometritis and 89% of cows without endometritis were confirmed pregnant by 300 days postpartum (P < 0.003). (For these two groups, 69, and 90% respectively, became pregnant during the duration of the study). Pregnancy to first service percentage was lower (11 versus 36%; P = 0.001) for cows with than without endometritis, and these cows required more services before 50% became pregnant (3 versus 2; P = 0.006). In a second study using 22 cows in a university-owned herd, the prevalence of cytological evidence of inflammation was 100% at 2 weeks postpartum, and dropped to 89, 58, and 41% at 4, 6, and 8 weeks, respectively. Endometritis diagnosed by endometrial cytology late in the voluntary waiting period was highly prevalent and exerted a profoundly detrimental effect on subsequent reproductive performance, making this condition potentially extremely costly to the North American dairy industry.