Abstract
Ovarian activity and uterine involution of 34 postpartum dairy cows were investigated following the intrauterine administration of oxytetracycline (500 mg per tablet). The cows were divided into six groups by treatment: group A (n=6), no tablet; group B (n=6), two tablets within six hours after calving; group C (n=6), four tablets within six hours after calving; group D (n=6), two tablets at 24 hours after calving; group E (n=6), four tablets at 24 hours after calving; group F (n=4, retained placenta), four tablets within six hours or at 24 hours after calving. The following results were obtained: 1) No significant defferences were detected in the times of the first corpus luteum recognition and estrous return among the six groups. 2) Involution times of uterine width of the pregnant side in groups B and E, and cervical width in groups C and E were significantly earlier (P< 0.05) than those of group A. 3) Most of the lochiae on day 1 (calving day=day 0) to day 3 in groups B, C, D and E were lighter in color than those of group A, but all lochiae on and after day 3 in group F changed to dark red. 4) Bacterial counts in the lochiae of groups B and C fluctuated slightly for two days following the administration. However, a decrease in bacterial number in groups D and E was evident for one or two days. 5) No peculier lochial odor due to retained placenta could be detected in group F.
