Spermatogenesis and Sperm Maturation in Male Poultry: Targets for Improving Male Reproductive Performance1

Spermatogenesis and sperm maturation are complex processes which are affected by a myriad of endocrine, paracrine and neural factors. In birds, regulation of testicular and excurrent duct growth, maturation and function are only poorly understood. As the quality and quantity of sperm produced may be altered at any of several points during sexual maturation, spermatogenesis or during extragonadal sperm maturation, understanding these processes could have profound effects on male reproductive performance. In this paper, the effects of transient prepubertal hypothyroidism on adult testis size and sperm production, as well as the effects of the sperm degeneration allele on sperm function, will be discussed. These two models strongly suggest that male reproductive performance can be altered during development, positively by increasing sperm production via transient hypothyroidism and negatively by altering the pattern of excurrent duct differentiation and, ultimately, function. In the future, breeders may be able to exploit the genetic components of these traits to increase the reproductive capacity of breeder males.