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

•Despite heat and cold treatments being effective in mice and rats to reduce male fertility they are not effective in ram lambs.•A Busulfan dose of 4 mg/kg did not deplete spermatogonia and caused significant short term reductions in blood parameters.•Very young lambs are highly sensitive to the effects of testicular Irradiation.•Sertoli cells in the seminiferous tubules were highly susceptible to irradiation which is in contrast to older animals.•Permanent infertility was induced (testicular atrophy) in 50% of animals treated with high irradiation doses.