Regulation of postnatal development of testes and its association with puberty and fertility -A review

Abstract

Indigenous bull breeds attain puberty late in life when compared to the breeds of <italic>Bos taurus</italic>. Cross breeding between <italic>Bos taurus</italic> and <italic>Bos indicus</italic> has decreased the age at puberty and increased the total semen production period of bulls. However, some of the drawbacks like impaired semen production, poor libido, and low freezability are common among the crossbred bulls in India. Leydig and Sertoli cells are the most important non–germinal cells of testes that are essential for sperm production. The development and differentiation of these testicular cells occurs during postnatal period in bull calves and are dependent on the transient rise in gonadotropins, insulin–like growth factor 1 (IGF–1), and other growth factors. Administration of gonadotropins or gonadotropin–releasing hormone (GnRH) before the transient rise initiates the multiplication of Leydig and Sertoli cells, and results in hastened onset of sexual maturity, increased testicular weight, sperm output, and number of germ cells. Supplementation of high–energy diet during the period of 2–6 months is essential as it increases the IGF–1 release that further acts to release GnRH and development of testicular non–germinal cells. This review highlights some of the developments made with respect to regulation of postnatal development of testes, early detection of fertility, and ways to augment the sperm production capacity.