In the cow, cesarean section delivery is often followed by retention of fetal membranes. Hypothetically, the retention of fetal membranes could be prevented by intraplacental injections of the enzyme collagenase. However, the infusion of this potent proteolytic enzyme into a uterus traumatized by surgery can lead to uterine damage, including perforation. Thus, the objective of this research was to evaluate tolerance of intraplacental treatment of bacterial collagenase. A cesarean section was performed on 10 experimental cows undergoing induced delivery or diagnosed with dystocia. During the surgical procedure, 200,000 units of bacterial collagenase in 1 L of saline were infused via the umbilical arteries. A cesarean section was also performed on control cows (n = 25) affected by dystocia, but these received no collagenase. The collagenase-treated cows showed no clinical or laboratory signs of abnormality over a 3- to 4-wk observation period post treatment. When membrane retention time was set at 36 h post surgery, 20% of the experimental cows and 60% of the control cows had retained the fetal membranes. It was concluded that intraplacental administration of collagenase during cesarean section is safe. However, treatment effectiveness and economic benefits for commercial application need further study. (C) 1997 by Elsevier Science Inc.