Histological Study of the Development of the Testis of the Ram

Abstract

Individuals from a group of 12 Hampshire ram lambs were serialized and castrated at bi-weekly intervals from two to 26 weeks of age. Seven Southdown rams were used to secure testes for ages of nine to 22 weeks. At the time of castration the body weight and age of the ram were recorded as well as the weight and volume of each testis and each epididymis. The center portion of each testis and epididymis were fixed in Bouin's fixative, sectioned at five microns and stained with Heidenhain's Iron Hematoxylin. The development of the testis was evaluated by its weight and volume, diameter of its seminiferous tubules, and the number of each cell type (spermatogonia, primary and secondary spermatocytes, spermatids and spermatozoa) per tubule. The diameters of 25 randomly chosen seminiferous tubules were measured and the cells were then counted. Qualitatively, primary spermatocytes were present in the Hampshire ram lamb at four weeks of age while these cells were found for the first time in the Southdown lamb at nine weeks of age. A few secondary spermatocytes were found in the ten week old Hampshire ram but not until 18 weeks in the Southdown. Spermatids were seen for the first time in the 22 week old Southdown and at 24 weeks in the Hampshire. It was concluded that rams were fertile when they were five and one-half to six months of age. Quantitatively, the volume of the testis increased directly with testicular weight. The diameter of seminiferous tubules increased in a curvilinear (quadratic) manner when compared with age, bodily weight or testicular weight. Some breed differences were found in the rate of increase in cellular types in relationship to age, body weight, and testicular weight. Copyright © . .