Factors affecting spermatogenesis in the stallion.
Abstract: Spermatogenesis is a process of division and differentiation by which spermatozoa are produced in seminiferous tubules. Seminiferous tubules are composed of somatic cells (myoid cells and Sertoli cells) and germ cells (spermatogonia, spermatocytes, and spermatids). Activities of these three germ cells divide spermatogenesis into spermatocytogenesis, meiosis, and spermiogenesis, respectively. Spermatocytogenesis involves mitotic cell division to increase the yield of spermatogenesis and to produce stem cells and primary spermatocytes. Meiosis involves duplication and exchange of genetic material and two cell divisions that reduce the chromosome number to haploid and yield four spermatids. Spermiogenesis is the differentiation without division of spherical spermatids into mature spermatids which are released from the luminal free surface as spermatozoa. The spermatogenic cycle (12.2 days in the horse) is superimposed on the three major divisions of spermatogenesis which takes 57 days. Spermatogenesis and germ cell degeneration can be quantified from numbers of germ cells in various steps of development throughout spermatogenesis, and quantitative measures are related to number of spermatozoa in the ejaculate. Germ cell degeneration occurs throughout spermatogenesis; however, the greatest seasonal impact on horses occurs during spermatocytogenesis. Daily spermatozoan production is related to the amount of germ cell degeneration, pubertal development, season of the year, and aging. Number of Sertoli cells and amount of smooth endoplasmic reticulum of Leydig cells and Leydig cell number are related to spermatozoan production. Seminiferous epithelium is sensitive to elevated temperature, dietary deficiencies, androgenic drugs (anabolic steroids), metals (cadmium and lead), x-ray exposure, dioxin, alcohol, and infectious diseases. However, these different factors may elicit the same temporary or permanent response in that degenerating germ cells become more common, multinucleate giant germ cells form by coalescence of spermatocytes or spermatids, the ratio of germ cells to Sertoli cells is reduced, and spermatozoan production is adversely affected. In short, spermatogenesis involves both mitotic and meiotic cell divisions and an unsurpassed example of cell differentiation in the production of the spermatozoon. Several extrinsic factors can influence spermatogenesis to cause a similar degenerative response of the seminiferous epithelium and reduce fertility of stallions.
Publication Date: 2006-05-27 PubMed ID: 16728209DOI: 10.1016/s0093-691x(97)00353-1Google Scholar: Lookup
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Summary
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This research paper extensively explores the process of spermatogenesis in stallions and the variety of factors that can modulate it. It underlines the potential impacts of various environmental and intrinsic elements that can lead to degeneration of germ cells and subsequently reduced fertility in stallions.
Spermatogenesis Process
Spermatogenesis includes three significant phases:
- Spermatocytogenesis: In this initial phase, mitotic cell division leads to an increased yield of spermatogenesis. It results in the production of stem cells and primary spermatocytes.
- Meiosis: This second phase involves duplication and exchange of genetic material coupled with two cell divisions. This reduces the chromosome number to a haploid, leading to the creation of four spermatids.
- Spermiogenesis: In the final phase, there is differentiation of spherical spermatids into mature spermatids without any division. The mature spermatids are then released from the luminal free surface as spermatozoa.
This complete cycle takes approximately 57 days in horses, with the spermatogenic cycle itself lasting around 12.2 days. This cycle, combined with the three major divisions of spermatogenesis, greatly aids in quantifying spermatogenesis and germ cell degeneration process.
Factors Influencing Spermatogenesis
Several factors might affect the rate and quality of spermatogenesis:
- Daily sperm production can be influenced by the degree of germ cell degeneration, age, puberty development stage, and also the season of the year.
- The number of Sertoli cells, the quantity of smooth endoplasmic reticulum in Leydig cells, and the total number of Leydig cells also affect sperm production.
- Several external factors such as elevated temperature, deficiencies in the diet, use of androgenic drugs such as anabolic steroids, exposure to metals like cadmium and lead, x-ray exposure, dioxin, alcohol, and infectious diseases can induce spermatogenesis dysregulation. Remarkably, distinct factors might elicit similar temporary or permanent detrimental responses. This degenerative response often leads to the formation of multinucleate giant germ cells, reduction in the ratio of germ cells to Sertoli cells, and an overall adverse effect on sperm production.
These extrinsic factors significantly contribute to reducing stallions’ fertility by influencing the spermatogenesis process.
Cite This Article
APA
Johnson L, Blanchard TL, Varner DD, Scrutchfield WL.
(2006).
Factors affecting spermatogenesis in the stallion.
Theriogenology, 48(7), 1199-1216.
https://doi.org/10.1016/s0093-691x(97)00353-1 Publication
Researcher Affiliations
- Department of Veterinary Anatomy and Public Health College of Veterinary Medicine, Texas A&M University College Station, Texas 77843, USA.
Citations
This article has been cited 11 times.- Orsolini MF, Meyers SA, Dini P. An Update on Semen Physiology, Technologies, and Selection Techniques for the Advancement of In Vitro Equine Embryo Production: Section I. Animals (Basel) 2021 Nov 13;11(11).
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- Madeira FF, Alevi KCC, Castro NFDC, Vilamaior PSL, da Rosa JA, Azeredo-Oliveira MTV. Reproductive Aspects of Chagas Disease Vectors: Evidence of Transcriptional Activity during the Nucleolar Persistence Phenomenon in the Spermatogenesis of Triatomines. Am J Trop Med Hyg 2019 Sep;101(3):602-604.
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- Ohrt MM, Ing NH. Supplementary L-arginine can enhance reproductive parameters and outcomes in large mammals. Front Vet Sci 2025;12:1740399.
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