Luteinizing hormone, testosterone and total estrogens response to exogenous GnRH in crossbred bulls with differing semen quality

The present study aims to investigate the Luteinizing hormone (LH), testosterone and total estrogens response to exogenous gonadotropin-releasing hormone (GnRH) in adult crossbred bulls with differing semen quality. Fourteen adult crossbred bulls of differing semen quality were selected and treated with 10 µg of GnRH (Buserelin acetate) intramuscularly. Blood samples of the bulls were collected at an interval of 30 min commencing 1 h prior to GnRH treatment until 4 h post-GnRH treatment and thereafter, at an interval of 1 h for the next 3 h. The endocrine response in terms of peak values, area under the curve, and the time taken to attain peak values for LH, testosterone, and total estrogens were evaluated in all the bulls. The mean±SEM peak levels of LH, testosterone, and total estrogens were found to be 150±24.1, 5.3±0.69, and 0.07±0.01 ng/mL, respectively. The mean±SEM area under the curve of LH, testosterone, and total estrogens were found to be 392±51.3, 23.5±3.4, and 0.32±0.04 ng/mL× h, respectively. The relationships between hormonal responses (LH, testosterone, and total estrogens) and semen quality were analyzed using the linear regression method, which provided non-significant (P>0.05) results. This study indicated that the gonadal and pituitary hormonal response to single exogenous GnRH treatment may have no relationship with the semen quality of crossbred bulls.