ABSTRACT
The present study utilized 6 sexually mature native Egyptian bulls raised in the National Research Center Farm, nearby Cairo. Bulls were used for collection of a single semen ejaculate / week for a period of one year using artificial vagina. Sexual behavior was measured in term of reaction time and number of mounts per ejaculate. Semen samples were immediately examined after collection for physical, microscopical and chemical properties. Jugular blood samples were collected once in the middle of each month from each bull for assaying testosterone value [Radioimmunoassay]. Results obtained from collection of 312 ejaculates revealed that native Egyptian bulls have reaction time of 41.22 sec and number of mounts per ejaculate of 1.31 with the best parameters during autumn and the poorest parameters during winter. Ejaculate volume [ml.], sperm cell concentration [X10[6] /ml] averaged 3.39, 1181.96 and 4051.180 with the highest values during autumn and the lowest values during spring. Mass motility [0-5] averaged 3.66 with the best value during spring and the lowest during winter. Individual motility and alive sperm percentage were 76.11 and 88.0%, respectively with the highest values during autumn and the lowest values during winter. Sperm abnormalities averaged 12.63% with the best percentage during summer and the highest value during winter. Initial seminal fructose and citric acid concentrations averaged 764.32 and 384.34 mg/dl, respectively with the highest concentrations during autumn and the lowest values during winter and summer, respectively. Sodium and potassium ion concentrations were 180.60 and 108.03 Meq/1, respectively with the highest values during autumn and February, and winter and February, while the lowest values were obtained during spring and June, summer and September, respectively. Plasma testosterone value averaged 4.07 ng/ml with the highest value was obtained during autumn and the lowest value during spring. In conclusion, native Egyptian bulls showed sexual behavior, semen characteristics and plasma testosterone values comparable to those parameters of universal breeds, however, highly significant seasonal and monthly variations were evident with the best results obtained during autumn season and during November and December