[Objective] The research aimed to study the reproductive health of breed- ing bull after infecting Mycoplasma wenyoniL [Method] The blood and semen quality of breeding bull before and after drug treatment was studied by the methods of blood routine examination and breeding soundness examination （BSE）. [Result] Be- fore the treatment with primaquine phosphate, slight anaemia was seen in diseased bull and a lot of M.wenyonfi were seen on blood smears. The scrotal wall of dis- eased bull swelled, testis was softened, the semen quality was reduced, semen quality was decreased and the proportion of primary and secondary deformed sperms was increased. After drug treatment, M.wenyonfi quickly disappeared from blood and the clinical systems were gradually alleviated, so BSE of breeding bulls after one month was passed. [Conclusion] The research laid the foundation for fur- ther study on the relationship between M.wenyonfi and the reduction of bull＇s repro- ductive functions.
