The latest I had one drop was 19 months. Now, oddly, this colt had both testicles when I checked for the first time, which was four months old. Shoulda had him gelded, then!
After he was 6 months, when I was going to get it done, they had disappeared, both of them.
When he was 19 months old, first one, then a week later, the other dropped. They were very small when they dropped, but quickly grew quite large.
Yes, the single testicle that has just dropped can be very small and hard to find, especially at birth as they are like tiny beans or tubes in there.
I had one stallion that had one testicle from the time I got him (4 mo.) and never got the other, not when he was 4.5 years old, even, so I had him gelded. The visible and palpable testicle was fairly small about the size of a walnut til he was 2, and then it grew about the size of a large plum. My vet agreed this was a problem, and he palpated him several times. One came off normally, but the other was quite deep in the abdomen and required extensive and invasive surgery.
None of his sons had the same problem, they all three had their testicles at birth and were gelded normally (yes, I bred my monorchid/cryptorchid and I would not do it again now that I have learned what I know now, but I was honest and I did geld his babies).
In the case of purchasing an older stallion, I guess you are at the mercy of the breeder as to whether he dropped early or late, but I would choose one that had dropped before by the time he was a yearling and no later, if I had to do it again.
Liz M.
