Factors affecting testis weight in normal and cryptorchid horses.

This research examines how testicle size in horses are influenced by age, breed, and by conditions such as cryptorchidism, where one or both of the testes fail to descend.

Methodology

• The study involved testing different breeds and ages of normal and cryptorchid horses.
• The testes were collected and weighed after they had been dissected from the epididymis, the tube that carries sperm.

Testicular Growth in Normal Horses

• The study found that in normal horses, testicular growth does not occur significantly until the second winter of their life.
• Despite the body of the horse reaching nearly its full mature weight by the end of the first winter, the testes do not show significant growth at this stage.

Testicular Size in Unilateral Cryptorchid Horses

• In unilateral cryptorchid horses, where only one testis has descended, the scrotal testis (the descended one) tend to be larger than those of normal stallions. This difference in size can sometimes be exceedingly large.
• However, there are also instances where small scrotal testes are observed in unilateral cryptorchid horses.

Impact of Cryptorchidism on Testicular Growth

• The research reveals that testes that remain inside the body (inguinal testes) display some growth during the horse’s second winter. However, it is hard to analyze the growth beyond this stage due to the transient nature of most cases of inguinal cryptorchidism.
• The abdominal testes in horses (those that remain in the body’s abdomen) do not appear to increase in size as the horse ages. But in cases where the scrotal testis is removed from a unilateral abdominal cryptorchid horse, the remaining abdominal testis experiences marked growth or hypertrophy.