Q: I have a 24-month-old Azteca (in this case, Andalusian x APHA) colt that has dropped only one testicle so far. He had two normal-appearing testicles at birth, and both of them withdrew above the inguinal ring before he was a year old.

This past winter, when he was about 20 months old, his left testicle dropped and appears normal, although rather large for his age. My vet palpated his inguinal ring recently and found it to be still open and about 3 inches in diameter, but could not palpate the other testicle.

I would eventually like to use this colt as a breeding stallion. I have not collected him yet to evaluate his sperm quantity and quality. There are no other known cryptorchids from the Andalusian sire. The APHA dam has only one other foal, a colt by the same sire, with two normal testicles at the age of one year.

I have sought advice on the chance of the other testicle dropping, as well as on the heritability of the condition, from a variety of sources. A friend who has been breeding Paints for many years says that it is not unusual for that breed to retain a testicle until the age of 30-36 months