Effect of ecbolic therapy on uterine involution, disease and reproductive performance in dairy cows
Postpartum uterine disease continues to be a significant factor in reproductive efficiency in dairy cattle. Cows with postpartum uterine diseases require more inseminations per conception, have reduced ovarian activity, and are more likely to be culled for reproductive reasons than normal cows. Poor uterine involution predisposes the cow to endometritis, pyometra, and delayed onset of ovarian activity. Therapies which increase the frequency, duration and strength of uterine contractions in the postpartum period might enhance uterine involution, thereby improving reproductive performance. This thesis is an investigation of the effect of two uterine ecbolic therapies, oxytocin and prostaglandin F2[alpha] on uterine involution, prevalence of uterine disease, and reproductive performance. This thesis is also an investigation of persistence of uterine oxytocin receptors during the first week after calving. Uterine tissues (from day 0 to day 7) were fixed in formalin, embedded in paraffin and slides were prepared for immunohistochemistry. Purified polyclonal rabbit anti-human oxytocin receptor antibody was used as the primary antibody. Immunoreactivity was scored semi-quantitatively based on distribution of receptors in various layers. To assess the efficacy of ecbolic therapy in postpartum cows, a randomized double blinded clinical trial was conducted at the Elora and Ponsonby Research Stations. 118 post-partum dairy cows between 1 st and 5th lactation with normal parturition and drop of fetal membranes were included in the study. The cows were randomly divided into three treatment groups - oxytocin, prostaglandin, and control. Cows were monitored from day 3 to day 63 by performing the following procedures: rectal palpation, vaginoscopy, and Metricheck® examination (twice weekly); transrectal ultrasonography starting day 7 (once weekly); endometrial cytology (once a week up to 30 days and thereafter once in two weeks until 63 days postpartum). Blood samples were collected for measurement of progesterone on days 21, 35, 49 and 63. Herd breeding records were obtained to determine reproductive performance in treated and control cows. Oxytocin receptors were detected in different uterine tissue layers up to day 7. Neither oxytocin nor prostaglandin therapy during the first week postpartum had any significant effect on rate of uterine involution, prevalence of endometritis or reproductive performance, compared to untreated controls. A progressive' decrease in the weekly prevalence of endometritis was noticed in all treatment groups over the course of the study.