The relationship between mastitis and retained placenta in a commercial population of holstein dairy cows

The relationship between retained placenta and mastitis was studied in a population of dairy cows on commercial farms. Only mastitis cases which occurred shortly after calving were studied. The cows with retained placenta were at a higher risk of developing non-severe mastitis (relative risk = 1.5) and at a much higher risk of developing severe mastitis (relative risk = 5.4). There was a differential effect of long-term (> 6 days) versus short-term (< 5 days) retained placenta. It is suggested that the relationship between retained placenta and mastitis is moderated by the prepartum peripheral leukocyte activity.