Veterinary Physiology-III

SEMEN

• It is a highly concentrated fluid with low volume.
• Average volume is 0.5ml in cocks with a concentration of 4 billion (4x10⁹) sperms per ml.
• The sperm head is narrow and long with a small acrosome.
• Poultry sperms are immotile before ejaculation and become motile after ejaculation. The vagina of the hen acts as sperm storage tubules which help to supply viable sperms to fertilize the oocytes for many days.
• Spermatogenesis involves mitotic division followed by meiosis to produce haploid cells. The spermatogonium produces spermatocytes and spermatids; spermatogenesis occurs at the core body temperature of 40-41C.
• Gonadotropins and gonadal steroids are essential for spermatogenesis
• Testosterone produced by Leydig cells under the regulation of LH has a role in spermatogenesis.
• The immotile sperms after spermiation (release from seminiferous tubules) are carried by seminiferous fluid through the tubules towards the excurrent ducts of testes. Sperm taken from excurrent ducts have fertilizing ability.
• Poultry sperm do not undergo capacitation before fertilization.
• Polyspermy is very common