Estrus synchronization and fertility in post-partum dairy cattle after administration of human chorionic gonadotrophin (HCG) and prostaglandin F 2α analog

Abstract

Human chorionic gonadotrophin (hCG) plus PGF 2α was compared with GnRH plus PGF 2α for estrus synchronization of dairy cows. There were 3 treatments: GnRH analog (Buserelin, 12.6μg) plus PGF 2α analog (Cloprostenol, 150μg) 6 d later (GnRH+PGF[Day 6]); hCG (2000 IU) plus PGF 2α 9 d later (hCG+PGF[Day 9]); and hCG plus PGF 2α 6 d later (hCG+PGF[Day 6]). Treatment occurred either Days 55 to 90 Or Days 91 to 135 post partum. For responses during the first 10 d after PGF 2α administration, estrus synchronization (P=0.24), efficacy (percentage of treated pregnant; P=0.20) and conception (percentage of inseminated pregnant; P=0.23) rates were not different among the 3 treatments. Cows treated between Days 55 and 90 had a higher rate (P<0.05) of detected estrus during this period (69% for GnRH+PG [Day 6], 70% for hCG+PGF[Day 9] and 72% for hCG+PGF[Day 6]) compared with cows treated between Days 91 and 135 (52% for GnRH+PGF[Day 6], 50% for hCG+PGF[Day 9] and 57% for hCG+PGF[Day 6]). Efficacy of treatment was higher (P<0.05) in animals treated between Days 55 and 90 (54% for GnRH+PGF[Day 6], 56% for hCG+PGF[Day 9] and 63% for hCG+PGF [Day 6]) compared to animals treated between Days 91 and 135 (36% for GnRH+PGF[Day 6], 35% for hCG+PGF[Day 9] and 47% for hCG+PGF[Day 6]). There were no significant differences in conception between Days 51 and 90 and Days 91 and 135. The interval between parturition-first AI with conception was significantly (P<0.001) shorter in GnRH+PGF (Day 6; 106 d), hCG+PGF (Day 9; 109 d) and hCG+PGF (Day 6; 103 d) treated cattle than in 106 untreated animals ( 136 d). Thus, GnRH plus PGF 2α or hCG plus PGF 2α treatments elicited similar effects in estrus synchronization, treatment efficacy, and conception rate in post-partum dairy cows.