Spermatogonia survival in young ram lambs following irradiation, Busulfan or thermal treatment

Abstract Many alternatives to surgical castration have been explored to induce short or long term infertility in male animals. Comparatively few have been carefully evaluated in very young production animals. A comparison of four treatments known to deplete testicular cells in rodents (heating, cooling, chemotherapy, radiation) was undertaken using ram lambs. Neither testicular cooling (0 °C) nor heating (45 °C) affected testis weights, tubule diameters or germ cell numbers. Low dose chemotherapy (Busulfan 4 mg/kg) treatment caused dramatic falls in white blood cells and platelets numbers which recovered within 3 weeks. Spermatogonia numbers were not significantly reduced (27% change). The impact of irradiation doses (0–15 Gy) delivered with high precision to the testis by a 6 MV photon beam was assessed by serial biopsies. Sertoli cell numbers were depleted by 90% at 3 weeks in 15 Gy treated testes. Spermatogonia were depleted 8 weeks after irradiation with 9 Gy, 12 Gy and 15 Gy. By 13 weeks, only in the 15 Gy treated testes were spermatogonia and Sertoli cell numbers lower. At 13 weeks testis atrophy resulted in 3/6 lambs irradiated with 12 Gy or 15 Gy. Irradiation of very young lambs clearly compromised testis function, thermal treatment was ineffective and busulfan treatment resulted in minimal effects.