Effects of cloprostenol and oxytocin on ultrasonographic changes of uterine horns in postpartum primiparous Hu sheep.

This study aimed to evaluate the effects of exogenous hormones on postpartum ultrasonographic changes of uterine horn in Hu sheep. 90 nulliparous Hu sheep were divided into three groups according to the number of lambs. Each group was further randomly subdivided into three groups (n = 10), a control group (sodium chloride), a PG group (cloprostol), and a PG+OT group (cloprostol + oxytocin). The effects of different treatments on ultrasonographic changes of uterine horn and reproductive performance of ewes were determined after the treatment. Then, 90 nulliparous ewes were divided into a control group, PG group, and PG+OT group according to hormone injections received. Each group (n = 30) consisted of 10 single, 10 twin, and 10 triple ewes. Changes in the levels of hormones P4, LH, FSH, and E2 in the serum of postpartum ewes, the time of the first estrus, and the conception rate were detected. Results showed that the higher the lambing rate, the slower the rate of ultrasonographic changes of uterine horn. The rate of ultrasonographic changes of uterine horn in the PG+OT group was faster than that in respective PG and the control groups. Caruncle diameter was not affected by the number of lambs or hormone treatment. After delivery, the concentrations of P4 and LH increased rapidly and remained at a relatively high level, while the concentration of E2 increased in all ewes. The PG+OT group had lower P4 concentrations compared to the control group, but higher LH, FSH, and E2 levels. The time to first postpartum estrus was significantly shorter in the PG+OT group, but differences in pregnancy rate were not significant. Thus, PG+OT treatment can significantly accelerate postpartum ultrasonographic changes of uterine horn, which can prepare postpartum ewes for the next reproductive cycle.