Epidemiological study of metritis in Michigan dairy cattle.

A prospective study using the Michigan National Animal Health Monitoring System was conducted to determine factors that affect the incidence of metritis in Michigan dairy herds. Data on herd management, disease, and environmental risk factors were collected from a stratified random sample of 97 herds with 7,835 cows for 12 months. Linear and logistic regression models were developed to assess the association between metritis and factors at the herd and cow level. Significant factors included retained placenta, dystocia, routine post partum examinations, herd size, and parity. Implications on the interpretation and use of results from herd- and cow-based analyses are discussed.