A hospital-based study of the relationship between retained placenta and mastitis in dairy cows.

We investigated the relation between retained placenta and mastitis in Holstein dairy cows admitted to the New York State College of Veterinary Medicine. Cows with retained placenta were three times more likely to develop mastitis during hospitalization than animals without retained placenta. Since the hospital population was not representative of the general population, the possibility of a bias existed; a large bias was not likely because most distorting variables occurred equally in animals both with and without retained placenta. The literature suggests that the relationship between retained placenta and mastitis may be mediated through activity of the peripheral leukocytes. Further research is necessary to test this hypothesis.