Effect of Gnrh Administration at Artificial Insemination and on Day 6 Post Insemination on Pregnancy Outcomes in Holstein Friesian Cows

Abstract

This study aimed to compare the effects of GnRH treated at artificial insemination (AI), at day 6 post-AI and at both times on pregnancy success in Holstein Friesian cows. The experiment was carried out at Aslam and Sons Dairy Farm at Dijkot, Faisalabad, Pakistan from February to June 2026. Eighty second parity cows were randomly divided into 4 groups (20 cows per group). G1 were the controls, G2 were treated with GnRH at AI, and G3 and G4 were treated with GnRH at AI and at 6 days post-AI. Each administration consisted of 5 mL of Conceptal intramuscularly, equivalent to 20 µg of buserelin. Artificial insemination was performed approximately 12 hours after the onset of natural estrus. Pregnancy diagnosis was performed using ultrasonography on days 28 and 45 post-AI to evaluate pregnancy establishment and maintenance. Overall, 45/80 cows (56.25%) were pregnant on day 28. Pregnancy rates were 45%, 60%, 55%, and 65% in G1, G2, G3, and G4, respectively; differences among groups were not statistically significant (χ² = 1.778, p = 0.620). Of the 45 initially pregnant cows, nine (20%) experienced subsequent pregnancy loss by day 45. Pregnancy loss was 33.33% in G1, 25.00% in G2, 18.18% in G3, and 7.69% in G4, with no significant difference among groups (p = 0.481). Maintained pregnancy rates per inseminated cow were 30%, 45%, 45%, and 60%, respectively (χ² = 3.636, p = 0.304). In conclusion, combined GnRH administration at AI and on day 6 post-AI produced the most favourable numerical outcomes for pregnancy establishment and maintenance. However, these differences were not statistically significant, warranting further investigation in larger studies.