Submitted to: Reproduction
Publication Type: Review Article
Publication Acceptance Date: 8/1/2005
Publication Date: 4/20/2006
Citation: Ford, J.J., McCoard, S.A., Wise, T.H., Lunstra, D.D., Rohrer, G.A. 2006. Genetic variation in sperm production. In: Ashworth, C.J., Kraeling, R.R., editors. Control of Pig Reproduction VII. Proceedings of the Seventh International Conference on Pig Reproduction, June 12-15, 2005, Kerkrade, The Netherlands. Society of Reproduction and Fertility Supplement 62:99-112.
Technical Abstract: In boars, the primary determinant of daily sperm production is number of Sertoli cells, which establishes testicular weight. The only breed comparison of fetal testicular development in boars contrasted two diverse breeds, White composite (WC, Landrace-Yorkshire) with Meishan, a Chinese breed that undergoes pubertal development at a young age and has small testicular size. During the prenatal period, the pattern of change in testicular development is similar in these two breeds with both having their greatest proportion of proliferating Sertoli cells at 90 days of gestation, and with WC boars possessing more Sertoli cells and greater mass of seminiferous tubules during the last one-half of gestation. During the first month of life, Meishan boars accumulate Sertoli cells and mass of seminiferous tubules at a greater rate than WC boars and undergo terminal differentiation of Sertoli cells at a younger age. Postpubertal boars, within each breed and crossbreds of the two breeds, with small testicular size have increased circulating concentrations of follicle-stimulating hormone. No direct breed comparisons of testicular development are apparent for postpubertal boars of other breeds. Accepting the limitations of data reported from different laboratories, Piau boars reach puberty at an older age and have a greater proportion of their testes occupied with seminiferous tubules than Meishan boars; both breeds have small testes. A gene or genes on the X chromosome code for small testicular size in Meishan crossbred boars; genetic determinants of testicular size and sperm production in other breeds remain to be identified.