Five mature rams of four years old were injected intramuscularly (I/M) once as 200 mg/ 10kg B.W. Terramycin long Acting (TLA) for each. Semen samples were collected from each ram 3 weeks before injection as a control samples, at 2nd, 3rd and 7th day after injection then weekly for up to 5 weeks. Immediately after collection semen samples were evaluated for semen characteristics. Also some reproductive performance and the body temperature of the male had been measured all over the experiment. Also, each semen sample was subjected to bacteriological examination where colonies were counted and subjected to biochemical identification. The obtained results revealed that significant reduction in semen volume and percent of individual motility, whereas there was no detectable significant effect was shown in sperm concentration. A significant reduction in the percent of coiled tail was proved at the 7th day post treatment, where as TLA injection did not evoke any effect on percent of live spermatozoa, acrosomal integrity, the reaction time and the scrotal circumference throughout the experiment. On the other hand, TLA was highly significantly increase the pH of the ram semen toward alkalinity (7.5+0.0) at the 4th week post treatment. While the osmotic pressure of the semen was decreased non significantly at 7th day. The body temperature was proved to be stable throughout the period of TLA treatment. A sharp reduction in the total bacterial count was obtained in the 3rd day after TLA injection, also the bactericidal action of TLA on the isolated E.coli and Staphylococci was nearly the same. In conclusion, Oxytetracycline long acting can be safely used in treatment of Barki rams, but during breeding season precaution should be taken to avoid over use.