Hello! I castrated my horse at 10 and he was a real difficult stallion. Most of the time by 10 it’s already quite late to change their attitude but castrating them will make them be a little more chill and easier to work with. They tend to lose the stallion neck a little, but minus that they just become easier to work with. Just make sure to keep his sheath extra clean. It’s definitely not too late for anything! Not sure what your trainer is on about!
Hey! I had a horse in my stables that was castrated when he was 10, he stayed exactly the same, beautiful coat, super energy, the only diference was he was much calmer with other horses!
But as Caoimhe says they are all diferent..
Hope it helps
Every horse is different. Some horses stay the same, some get extremely fat, some get lazy. It really depends on how much testosterone the horse has. You would be best asking advice from your local vet.