Effect of subclinical uterine infection on cervical and uterine involution, estrous activity and fertility in postpartum buffaloes

Nili-Ravi buffaloes (n=29) that calved normally between August and November and did not develop any clinical reproductive disorder after calving were studied for the incidence of sub-clinical bacterial infection of the uterus and its effects on postpartum reproductive efficiency. The incidence of subclinical uterine infection was 24% (7/29). Involution of the cervix and uterus was slower (P < 0.01) in the infected group than in the normal group (45.6 vs 31.1 days and 46.3 vs 35.8 days), respectively. The mean diameters of cervix and gravid horn on Day 12 post partum and on completion of involution did not differ between buffaloes of the two groups. However, the rate of involution of the cervix and the gravid horn was lower in buffaloes of the infected group (2.2 vs. 2.7 mm/day and 2.6 vs. 3.2.mm/day). The mean interval to first post partum ovulation was similar in buffaloes in the infected (35.5 days) and the normal group (33.8 days). The life span of corpus luteum formed after first ovulation was shorter (11 days) in buffaloes of both groups than that of a normal estrous cycle (15 to 17 days). The incidence of silent ovulation was apparently higher in buffaloes of the infected group (83 vs. 60%) but the difference was not significant. For the first four months after calving, the mean interval to first postpartum estrus was longer in buffaloes of the infected group (73.0 vs. 47.7 days; P < 0.01). Similarly, the average service period was longer in buffaloes of the infected group (91.0 vs. 64.8 days; P < 0.05). The overall pregnancy rate for the first four months after calving did not differ between buffaloes of the two groups. We conclude that subclinical bacterial infection of the postpartum uterus delays the cervical and uterine involution which can, in turn, delay the occurrence of first postpartum estrus and prolong the service period in buffaloes. (C) 2001 by Elsevier Science Inc.