Traitements à base de progestagènes ou de mélatonine combinés à l’effet bélier chez la brebis Ouled-Djellal au printemps

To compare the effect of melatonin-based to progestagens with equine chorionic gonadotropin (eCG) based treatments used to improve the reproductive performance of Ouled-Djellal sheep breed, 829 ewes distributed among four farms (A, B, C, and D; n = 248, 351, 100, and 80; respectively) were monitored from March to October 2008. In farm B, progestagens improved fertility by 92.3% in ewes treated with medroxy- progesterone acetate (MAP) + eCG 400 IU, and by 84.1% in ewes treated with fluorogestone acetate (FGA) + eCG 500 IU, compared to 23.2% in the control group. The fertility rates obtained with melatonin implants after first mating in farms A and C were significantly lower than those obtained with progestagens + eCG (A: 40.9 vs 79.9%; C: 24 vs 70%). The fertility rate obtained with melatonin implants after first mating in farm A was higher (40.9%) than those obtained in farms C (24%) and D (17.5%). In farm D, melatonin implants improved total fertility compared to control (55.0 vs 17.5%, respectively). MAP + eCG 400 IU improved the conception rate at first mating in farms A (1.30) and B (1.70), whereas FGA + eCG 500 IU, and melatonin implants did not. Melatonin implants, in combination with the ram effect, and used at an early stage yielded good results that were similar to those obtained with progestagens.