Veterinary Andrology and Reproductive Techniques

Physical factors

I: PHYSICAL FACTORS

Irradiation

• Irradiation produces interference with spermatogenesis by injuring spermatogonia, spermatocytes and spermatids.

The spermatocytes are most sensitive to irradiation while leydig and sertoli cells are quit resistant.

• Steroidogenesis is not affected much by the X-rays. The testosterone level is maintained as such.

Hyperthermia

High ambient temperature will cause testicular degeneration which affects the spermatogenesis

• The causes for the elevation of testicular temperature are cryptorchid and ectopic testes, inguinal hernia, scrotal dermatitis due to irritants, chorioptic mange, myiasis in sheep and localized skin infections or wounds, contusions and haematomas of the scrotum and testes, prolonged body temperature as in certain infectious diseases and in prolonged high environmental temperature particularly associated with high humidity.
• Males that are unable to rise, often develops testicular degeneration and atrophy due to the prolonged elevation of testicular temperature from the testes being held close to the body.
• The temperature more than 41­⁰C has detrimental effect on spermatogenesis.
• The cells undergoing meiosis are more sensitive than resting sperm but there is no change in steroidogenesis.
• Late pachytene primary spermatocytes and early round spermatids are more sensitive.

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Hypothermia

• Spermatogenesis seems to be more resistant to cooling than to heat and the tunica dartos and cremaster muscle contract to protect the testes from the effects of cold.
• Damage to spermatogenic function is notices at the temperature below -25⁰ F.
• In hypothermia the stagnation of blood and resultant hypoxia is probably more damaging than to decrease in temperature.

Light

• The influence of light on control of spermatogenesis is brought through the capacity of it to control the pituitary gonadotrophin.
• The pineal body operated as a neuroendocrine transducer mediating light effects on the testes.
• The shortened photoperiod (below 12 hrs) decrease the capacity of the pituitary to release of gonadotrophin, possibly by reducing sensitivity to gonadal steroid hormone feedback. Thereby it brings about effect on spermatogenesis.

Low oxygen tension

• Spermatogenesis is severely impaired when adopted males are subjected to low oxygen tension at high attitude or in experimental chambers.

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