Retained Placenta in the Dairy Cow

Abstract

The exact mechanism which actually causes retention of the placenta~is not thoroughly understood. Comparison of histological sections taken at 4 to 5 hours after calving from cows which retain and those which cleanse normally cannot be distinguished from each other either in the villi of the fetal membranes nor in the maternal crypts of the caruncles. With retained placenta the normal separation of the fetal villi from the maternal crypts is interfered with and adhesions are formed. Two theories have been offered as basic etiologic
causes of retention. The first theory is that the result is due to imperfect contraction of the uterus, and the second is that the retention is a result of a proliferative placentitis such as seen in abortion caused by Bruce/la abortus. The placentitis theory does not hold up well because, in many abortions investigated today, there is no evidence of infection present. There seems to be a return to the older theory of uterine inertia or lack of motility and hormone dysfunction due to a variety of causes.