Veterinary Andrology and Reproductive Techniques

THERMAL CAUSES

• Elevation of the testicular temperature in conditions such as cryptorchid and ectopic testes; inguinal hernias; scrotal dermatitis due to, irritants, choriopic mange, myiasis in sheep, and localized skin infections or wounds; contusions and haematomas of the scrotum and testes; prolonged elevated body temperature as in certain infectious diseases and in prolonged high environmental temperatures, particularly associated with high humidity.
• Testicular degeneration is most common in tropical climates and involving breeds originating in the temperate zones.
• Bulls exposed to heat stress for 8 hours a day for 7 days resulted in a deleterious effect on semen quality reaching its peak at 2 to 3 weeks after the stress with recovery by 9 weeks.

 

• Rams maintained at ambient temperatures of 90⁰ F or above develop a marked drop in semen quality with about 10 percent motility and 70 percent abnormal sperm cells within a few weeks. Recovery was not complete until 2 to 3 months after normal temperatures were restored.
• High ambient temperatures will also cause lowered fertility due to testicular degeneration in boars.

TOP

Heat primarily affects the spermatids, the spermatozoa and the spermatocytes but usually does not affect the spermatogonia.

• Males that lie down for long periods of time such as bulls with bovine spastic syndrome, or males that are unable to rise, often develop testicular degeneration and atrophy due to the prolonged elevation of testicular temperature.
• When the scrotal temperature of bulls was raised to 38.4⁰C or 0.3⁰C below body temperature, the motility and percent of live spermatozoa in the semen decreased to zero by the second week.
• Damage to spermatogenic function occurred in beef bulls by low temperatures down to -25⁰F associated with winds of 60 miles per hour causing frostbite, necrosis of skin, scrotal dermatitis, heat, swelling, testicular degeneration and adhesions.

Heat has no effect on the Leydig cells.

TOP