Comparative Evaluation of Hormonal Treatments for Estrus Induction and Conception in Anestrous Postpartum Dairy Cows

Postpartum anestrus, along with the inconsistent efficacy of hormonal protocols, delays breeding and reduces profits for dairy farms.This study aimed to evaluate and compare the efficacy of four hormonal protocols targeting the follicular and luteal phases of the estrous cycle to induce estrus and improve conception rates in postpartum local Iraqi (Al-Janoubi) dairy cows, thereby reestablishing ovarian cyclicity between 60 and 120 days postpartum.A total of 40 anestrous cows were randomly assigned to four treatment groups (n=10 per group): T1 (Cloprostenol and Gonadorelin), T2 (Estradiol and Cloprostenol), T3 (Estradiol and Gonadorelin), and T4 (Cloprostenol alone).Estrus response, conception rate, and timing of estrus onset were recorded for all animals.Serum lutenizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations, estradiol (E2), and progesterone (P4) concentrations were measured using a Cobas e411.Pregnancy was confirmed by ultrasonography, with transabdominal scans employed when transrectal evaluation was not feasible.Estrus induction rates and conception rates showed significant differences (p = 0.048 and 0.0092, respectively).Groups T2 and T3 achieved 60% estrus induction, with conception rates of 33% and 67%, respectively.Whereas T1 and T4 had a 20% estrus response, resulting in no pregnancies.The onset of estrus occurred earliest in T2 (around 40 hours), intermediate in T1 and T4 (approximately 72 hours), and latest in T3 (about 144 hours).Although LH and FSH levels did not differ significantly among groups (p > 0.05), estradiol and progesterone levels were significantly higher in hormonally induced cows (p < 0.01), indicating luteal stimulation.In conclusion, among the tested protocols, the combination of estradiol and gonadorelin resulted in the highest conception rate, whereas estradiol with cloprostenol led to the earliest onset of estrus.In situations where estradiol is restricted, GnRH-or progesterone-based protocols remain viable alternatives.Maintaining an optimal body condition score (BCS 3-4) is essential for successful reproductive recovery in postpartum dairy cows.