Effect of season of birth and of hemicastration on the histology of the testis of 6-month-old lambs

Season but not hemicastration affected the cellular composition of the testis. Despite similar weight, the testicular histology differed markedly with season of birth. The number of Leydig cells and of Sertoli cells was greater in summer- than in winter-born lambs by factors of 2 and 1.5 respectively. Similarly the number of spermatogonia and their rate of production increased substantially in summer-born lambs. The rate of spermatid production was affected by both hemicastration and season. Season of birth exerted more modifications to testicular histology than did hemicastration.