Gonadotropin regimen and dose predict superovulatory ovarian response in Ouled Djellal ewes: a stepwise regression study

Abstract

This study aimed to evaluate the effects of gonadotropin regimen (PMSG alone vs. PMSG + GnRH or PMSG + hCG) and dose on superovulatory responses in 35 Ouled Djellal ewes during the breeding season. Intravaginal sponges containing 40 mg fluorogestone acetate were inserted for 14 days in all ewes. Two days before sponge removal, ewes were randomly assigned to seven treatment groups differing by regimen and dose. Outcomes were corpora lutea (CL) count, anovulatory follicles (AF), ovulation rate (OR), and serum progesterone (P₄). Associations were assessed using stepwise regression analysis. Ewes receiving PMSG + GnRH or PMSG + hCG exhibited stronger ovarian responses than those given PMSG alone. Final stepwise models explained 41.3% of variance in CL, 20.5% in AF, 27.10% in P₄, and 23.60% in OR. In each model, molecule type entered first and contributed more to model fit than dose, indicating that regimen exerted a greater influence than dose escalation. In conclusion, combining PMSG with either hCG or GnRH improves ovarian response parameters and overall model predictability compared with PMSG alone. These findings support evidence-based optimisation of superovulation protocols in Ouled Djellal ewes to enhance prolificacy, increase embryo yield, and accelerate dissemination of elite genetics in advanced breeding programmes.