The effect of retained placenta and metritis complex on reproductive performance in dairy cattle -- a case control study.

A study of the computer stored records of 293 dairy cows and 652 calvings reveals the effects of retained placenta and metritis complex on reproductive performance. The overall incidence rate of retained placenta was 11.2%. Retained placenta was 4.6 times more likely to occur following twin births than following single births. Most cases of retained placenta occurred during the fall. Forty-five percent of that seasonal increase was explained by an increased number of calvings. Metritis complex was diagnosed following 54.8% of retained placenta cases. Retained placenta alone did not significantly impair reproductive performance. Metritis complex, in the presence or absence of retained placenta, caused a significant (P</=0.05) increase in days open, services per conception, calving to first heat intervals and days from calving to first service. There is an indication (interaction P</=0.1) that cows with both retained placenta and metritis complex are more severely affected than cows with either retained placenta or metritis complex alone. The influence of retained placenta on fertility appears to depend on the proportion of cows with retained placenta that have metritis complex.