Hi, So after lots of begging from my daughter, we got a horse. Yes, I read up on their care, got a vet, and a trainer. We adopted a well trained 20 yr old quarter horse that is great for beginners. Then, about two weeks ago I decided to get a second horse that was larger so I could ride with my daughter. All was going great until my trainer left for two month vacation and the second horse arrived last week. Our second horse is a gelding and 16 yrs old. He is trained and very sweet with us. However, he has been acting a crazy fool since my mare came into heat. He is gelded, but is exhibiting stallion behaviors. My mare and the gelding have been kept seperated. They could see each other to get use to one another. Today, the mare pushed her way through a door to get in with the gelding. He has been mounting her (and doing the deed). His vet paperwork says he is gelded, he has no visible testicles. I did read that they can have a third one or have been proud cut. I am concerned that this is going to be a problem from now on. Should I wait until her next heat cycle to see if he still acts like a stallion? Or is this his behavior? He was used for breeding and gelded at least three years ago. So, other then having the vet check for hormone levels, what other things can I do? Is it going to hurt them to let them mate? I read about infection... Also, they are getting along fine now they are in the same pen together. Thank you!