Effect of infusion of uterine purulent exudate into the bovine uterus.

Purulent exudate from the uteri of two nonlactating Holstein cows with chronic pyometra was aspirated into a 50 cc syringe via an artificial insemination pipette. The two fractions were mixed, cultured, divided into 14 equal parts and infused into the uteri of 14 other nonlactating cows. All recipient cows had had at least one estrous cycle of normal length and were in the early luteal phase (day 4-8). On days 3, 7, 14 and 21 following infusion, the reproductive tract was examined per rectum, content of the uterus was cultured for bacteria, and endometrial condition was assessed by biopsy and histopathology. The lengths of the estrous cycles of the recipient cows were shortened P < 0.01) from 21 +/- .5 days to 13.3 +/- 1.4 days. Estrus was determined by palpation per rectum and/or observation. Over the experimental period, Pasteurella sp., Corynebacterium pyogenes and other diphtheroids were isolated from 64, 57 and 86% of the cows, respectively. An inflamed endometrium was associated (P<0.10) with the presence of Pasteurella sp. on day 7 following infusion. No other associations were found when the presence of bacteria, vaginal discharge, or short estrous cycles were compared. The infusion of purulent exudate apparently irritated the endometrium causing an early return to estrus rather than causing pyometra. It is probable that postpartum and lactational stress are involved in the development of pyometra.