Apparition of heats and LH preovulatory discharge in Djallonké ewes after heat synchronization with or without PMSG

Abstract

In order to study PMSG influence on the onset of heats and preovulatory LH peak, oestrus of 80 cyclic ewes were synchronized with vaginal sponges (fluorogestone acetate) during the dry and hot season. These ewes were divided into two groups (E and P) equal in size. At sponge removal, 14 days after insertion, each ewe from group P received 350 IU of PMSG, while group E did not undergo any treatment (control). Sexual behaviour in all ewes was observed every two hours using a vasectomised ram. One day after sponge removal, blood samples were collected every 2 hours for 4 consecutive days in 5 ewes from each group. These blood samples were used to assay the luteinizing hormone (LH) by RIA. Ewes were in heats earlier in group P than in group E (37.2 ± 13.3 h vs 43.7 ± 14.3 h for the period sponge removal - first signs of heats). However, heat duration (43.6 ± 20.8 h) was similar in both groups. LH preovulatory surge appeared sooner in group P than E (12.4 ± 1.5 h vs 19.5 ± 7.7 h after the oestrus). LH peak duration (10.7 ± 4.1 h) and its maximum value (90.5 ± 36.4 ng/ml) were similar in both groups. In general, heat and LH peak characteristics observed in Djallonké ewes seemed close to those previously reported in European breeds. In addition, PMSG hastened the onset of both oestrus and LH peak.