Effectiveness of Clinical and Hormonal Interventions for Managing Sub-fertility in Crossbreed Dairy Cattle in North Shoa Zone, Ethiopia

Abstract The purpose of this study was to evaluate estrus response and pregnancy rate in repeat breeder crossbred dairy cattle that were treated by exogenous reproductive hormones. Ninety-two repeat breeder cows/heifers with regular estrus cycle, no detectable reproductive tract infections, and no cystic ovary (rectal palpation and transrectal ultrasonography examination) were assigned to the treatment group, as GnRH *PGF2α group, single PGF2α, and double PGF2α injection group. The estrus response rate in repeat breeder dairy cows/heifers were significantly different (P < 0.05) by hormone treatment regimens, and it was 48.3% for the GnRH-PGF2α group, 72.7% for the single PGF2α and 86.7%, for double PGF2α. The estrus response rate was higher in cows aged 5 to 6 years than in cows aged ≤ 4 years and cows aged seven and above years old. Cows/heifers aged ≤ 4 years had a 6.1 (OR) times higher chance of responding, and those of 5 to 6 years old had a 19.5 times higher chance of responding to hormones compared to cows aged seven and above years old. The pregnancy rate was significantly (P < 0.05) greater in repeat breeder cows or heifers treated with the GnRH PGF2α regime than those in double and single PGF2α regimens. When compared to untreated cow or heifers, the chance of getting pregnant in repeat breeder cow/heifers treated with GnRH PGF2α, double, and single PGF2α regimen was respectively 13.9, 8.7, and 5.4 times higher (P < 0.05). Also, the chance of getting pregnant was 6.9 and 1.9 times greater (P < 0.05) in cows/heifers aged 5 to 6 and 2 to 4 years, respectively, compared to cows aged ≥ 7 years old. BCS of cows/heifers also had a significant influence (P < 0.05) on estrus response and pregnancy rate. According to the findings of this study, using exogenous hormone (GnRH with PGF2α or PGF2α alone) together with ultrasound scanning of ovarian status significantly improved estrus response and pregnancy rate.