Review: Spermatogenesis in the bull

Abstract

Spermatogenesis is a finely regulated process of germ cell multiplication and differentiation leading to the production of spermatozoa in the seminiferous tubules. Spermatogenesis can be divided into three parts: spermatocytogenesis, meiosis and spermiogenesis. During spermatocytogenesis, germ cells engage in a cycle of several mitotic divisions that increases the yield of spermatogenesis and to renew stem cells and produce spermatogonia and primary spermatocytes. Meiosis involves duplication and exchange of genetic material and two cell divisions that reduce the chromosome number and yield four haploid round spermatids. Spermiogenesis involves the differentiation of round spermatids into fully mature spermatozoa released into the lumin of seminiferous tubules. The seminiferous epithelium is composed of several generations of germ cells due to the fact that new generations of sperm cells engage in the spermatogenic process without waiting for the preceding generations to have completed their evolution and to have disappeared as spermatozoa into the lumen of the tubules. In bulls, the duration of the seminiferous epithelium cycle is 13.5 days. The total duration of spermatogenesis is 61 days, that is 4.5 times the duration of the cycle of the seminiferous epithelium. The spermatogenetic wave is used to describe the spatial arrangement of cell associations along the tubules. Several theories have been described to explain the renewal of spermatogonia. Depending on the model, there are five or six spermatogonial mitoses explaining the renewal of stem cells and the proliferation of spermatogonia. Daily sperm production and germ cell degeneration can be quantified from numbers of germ cells in various steps of development throughout spermatogenesis. Bulls have a lower efficiency of spermatogenesis than most species examined, but higher than that of humans.

Vascular wall injury and inflammation are key pathogenic mechanisms responsible for early testicular degeneration during acute besnoitiosis in bulls

“…However, this hypothesis requires further investigation. Moreover, whether bulls with oligospermia end up with testicular degeneration remains a possibility since the total duration of spermatogenesis in bulls is 61 days, and the duration of the seminiferous epithelium cycle is 13.5 days [36].…”

Climatic adaptation of bovine subspecies monitored by seminal characteristics during winter months in tropical region

“…Semen collections occurred in July, August and September. Yet, this study considered the last autumn month (May), as well as the first winter month (June), since total spermatogenesis in bulls lasts 61 days (Staub & Johnson, 2018), besides being a period of adaptation to the climatic conditions of the season.…”

Fertility maintenance in male oncological patients: current state and future perspectives

“…This process takes around 74 days, after which the morphologically mature, yet still immotile sperm cells spend 12 more days travelling within the intratesticular ducts, efferent ductules, but mostly within the epididymal duct. We distinguish two cell populations, which are absolutely essential in the process of spermatogenesis -supporting cells of Sertoli, providing mechanical support, nutrition and immunological protection (formation of the blood-testis barrier) for developing sperm, and interstitial endocrine cells of Leydig, responsible for the production of testosterone (Balko et al, 2017, Staub and Johnson, 2018).…”