Effect of ejaculation on plasma testosterone level of purebred native Egyptian bulls with emphasis on correlations with sexual behavior and semen characteristics

ABSTRACT

This is study was performed on 6 purebred mature native Egyptian bulls raised in the National Research Centre Experimental Farm nearby Cairo. To investigate the effect of ejaculation on plasma testosterone profile, blood samples were collected before [2 and 1 hr], during and after [1/2, 1, 11/2 and 2 hr] semen collection by means of an artificial vagina. Sexual behavior was evaluated in terms of the reaction time and number of mounts / successful ejaculate. Semen samples were examined and results were correlated with testosterone levels. Testosterone levels were assayed using the radioimmunoassay technique and data were statistically analyzed. Plasma testosterone value [ng/ml] averaged 4.07 +/- 0.43 in purebred native Egyptian bulls. Values obviously decreased after [3.64 +/- 0.17] than before [4.58 +/- 0.23] semen collection. Ejaculation induced more variations in testosterone levels during autumn and less variations during spring. Moreover, correlation coefficients between plasma testosterone level and sexual behavior and semen characteristics of native bulls were recorded. In conclusion, purebred native Egyptian bulls have a comparable blood plasma testosterone level to the universal breeds with obvious individual, monthly and seasonal variations