This study was carried out to determine the effects of zeranal implantation that had been used as an anabolic agent on the reproductive tract in the Brown Swiss male bulls.

Twenty three Brown Swiss bulls, 6-9 months old, were used in this study. These bulls were divided into three groups; Control, Group I and Group II. 36 mg zeranal was implanted subcutaneously .at the base of ear of bulls in Group I and Group II at the beginning of the experiment and the same dose was reimplanted to Group II 65 days after the first implantation.

Implantation of zeranal to the bulls induced histopathological changes on the reproductive tract, which included; reduction in the diameter of seminiferous tubules and delayed sperınatogenezis in the testes, inercaseel interductal conncctive tissue and muscular layer of the d. epididimis in the epididimites, augmented interalveoler connective tissue and reducecl alveoler development in the prostate, vesicular glands and bulbouretlrral glands.

It may be concluded that the implantation of zeranal would cause incufficiency at sexual breed function in bulls after 6 months of age.