I am interested in opinions on what age people like to geld their colts and why. Pros and cons of doing it early vs. waiting longer. Obviously colt “ish” behavior and naughty boys make the decision easy, but what if you have a perfect mellow gentleman?
Spring of yearling year, before the flies get bad.
We geld fall/winter after flies and before the return in spring. We are not set up for stallions and the fencing is not stallion secure and we don’t have enough boys to put geldings between them and mares/fillies. I also prefer the to geld before the mares catch their attention.
There are some physiological as well as mental differences. On the most part, horses that are allowed to be left as stallions, or gelded late towards maturity, will not grow to be quite as tall had they been gelded early. Also, once they develop a stallion’s crest, gelding them will most likely not make it go away. Plus the older they are before gelding, the more likely they are to retain a stallion’s attitude toward mares, if they ever express interest in them to begin with. However, one “benefit” I’ve noticed about horses that are gelded a little later (but before full maturity), is that they tend to be much cleaner in their stalls. 
It’s individual 
I’ve gelded as early as 7 weeks and as late as 8 and a breeding stallion. That lad was pretty mellow but after gelding he was even able to live in a mixed herd and has become a kids pony.
I prefer before weaning and after bug season
In North America, the market is not very open to raising stallions for sport that are not intended for breeding. We make the decision to geld or not to by age 2, and have done so to colts under age 1 due to behavioral issues.
IMO, unless your trying to produce a stallion for approval and breeding and you’re set up to do so, then don’t bother. Geld it by age 2.
There are certainly stallions who have been well mannered enough to keep the jewels even if they aren’t breeding. However, not many people want a stallion in their training barn. If you’re not well equipped in facility or people capable of raising, training and dealing with a stallion then don’t bother.
If you are interested in keeping a stallion with the hope that he’s good enough to be a “father” horse, and he looks to have potential for upper level sport, then go for it. If you look at stallions around the world…there are actually few who successfully do both sport and breeding…there is a reason for that.
Long story short…gelding a colt between age 6 mo and 2 yrs is the general window. Either do it in the spring as some have stated or in the fall…cool weather is best to reduce infection and the annoyance of flies and other pests.
I gelded my new colt at 9 months. I probably would have done it sooner if he had been mine before then. He was getting a little pushy and full of himself but between weaning (I know, late, wasn’t my choice) and gelding, now butter wouldn’t melt in his mouth.
As the above posters said, I think it is dependent on the individual.
I think it completely depends on the individual, and your intended end-use/market.
I bred my guy specifically for me, so he was gelded at six months (he was also a bit undersized, so we wanted him to use his groceries for height, not too much muscle). As an ammy hunter, I didn’t need or want to deal with a stallion.
One of his paddock mates was left entire till he was a yearling. By that point he was HUGE, and becoming aggressive. He had to be separated from the fillies and geldings in his age group. But he also made it clear he didn’t have the blood to be the top-flight GP jumper prospect he was bred to be. So off they came so he could become a childrens/ammy horse.
Another of his former paddock mates was entire till two/three (and may still be at four; I moved my squirt to be closer to my training facility). He is spectacular, and has actually even sired a colt out of a mare who just plain would not catch via AI. He has never shown any studdish-ness with humans, even when pasture breeding that mare.
So three colts born within 18 months and raised in the exact same environment = three different gelding dates.
I’ve never had the luck of a colt who was sweet. They have all turned HUGE PITA’s. Along with all the glorious stallion behaviors of rearing, striking, biting, ugh!
Soon as they realize “hey! I’m a GUY!” off with them. Late fall before ice & snow is my favorite time, but I’ve had to do it in fly season at a little over a year, because the behavior just wouldn’t last till fall. My vet says there is so little chance of complications in our area it’s no issue, just geld when you need to.
I don’t like to geld early, because I’m hoping against hope that this colt will be the sweetheart. I’m just delusional. My 3 year old certainly had the stallion potential, but he’s a handful even as a gelding, although of course getting better with age and now a little bit of work.
Hats off to professional stallion raisers. I truly don’t know how you manage it.
I think you have had good responses here already… It depends, both on the individual, and on his intended use and lifestyle.
Since my horses run together as a herd (especially in the winter), recently I have gelded early, around weaning time, especially if the horse is destined to be a gelding anyway, and a show horse. When racing, I tended to leave them colts until they told me they wanted/needed to be gelded to gain better early maturity. Last year, my one and only foal was a colt, destined to be a show horse/hunter/jumper, was gelded at 5 months. He is big, not only tall, but BIG bodied. I didn’t want him getting coarse or overdeveloped. He was also a bit coltish, early. The surgery is so easy at this stage, done standing, took 20 minutes by my skilled vet of choice, so easy to recover from, few complications. Plus, perhaps it will make him grow even taller, maybe 16.3 instead of 16.2. The other bonus is that he gets to remain with his friends and family, in the mixed herd, and grow up that way. I think this is very important to his social development. His dam is OLD, and not long for this world. He has made new friends, who look after him, play with him, help him become a functioning herd member. He weaned himself naturally, as he has lost interest in his dam, and spends more time with his friends. The herd teaches him better manners than any human could. His manners are impeccable.
My only colt was gelded the spring he turned one only because I have a 8 year old coming of the track that needed his removed. My colt was super sweet and never gave me a bit of trouble and he might have lasted longer as a colt if I didn’t already have the vet coming to do one. He was not nice enough to be a stallion though and there was really no reason to keep him in tact.
I left my colt intact until two; he was a perfect gentleman in every respect, but then one day he noticed the girls and the call was made to my vet. He was still easy to handle but I just didn’t want to deal with it, and had no intention of breeding. This may not be research-supported, but he developed such a lovely presentation. Just looks more masculine, if that makes any sense, through his neck and jaw. He has continued to grow and is nearing 16.2 now. I would have been happy if he stopped at 16!
We geld at about 12 months. We wait to limit growth, don’t want them hugely tall. We breed or buy for ouselves, not the market. We KNOW horse will be at least 16H with their breeding. Don’t want them 17H and above, just too big for our uses.
This late gelding has worked pretty well for us that way. We have not had any obnoxious colts, all are handled twice a day from birth. After weaning they are turned out with the older gelding who teach them manners, herd status, and play hard with the colt if he needs that. These colts do not seem interested in the mares, do not watch them or call to them before their gelding time arrives. Mares always are separated by at least one field.
As these colts age they seem to be very confident in new settings, facing things they never saw before, are bold horses to compete with, forward. Totally obedient, easy to handle, though like any young horse they can act dumb now and again, ask “Are you sure I can’t be the boss now?” They accept authority, do as requested when I say “Nope, people are always the boss”. We have two that will get the others behind them if presented with “the unknown”. I see them acting protective, like today with wild geese in the field. Horse approached geese and then chased them so they flew off. He felt he had done well!
Mine have lovely necks, not cresty, very flexible in work. We are really happy with the boys using the later age for gelding. They are turned out with mares after gelding, since they will eventually be working closely togtheer when used as Driving horses. No bullying the girls or being annoying. Mixed turnout works fine here, none of the “my mares” between the boys either.
Glad we have the older geldings to run with our colts before and after gelding. The older horses do a lot of the colt training in daily turnout, keep him civil, to make our handling work much easier.
We geld our colts as soon as they drop, usually around 4-6 months old. I want them to never realize they were born boys. 
Gelding mine on 4/2. He will be 8 mos. He’s still a sweetie, but I don’t want a stallion and it needs to be done before it gets too hot and the bugs get bad. I generally do it any time from weaning to 18 mos. depending on the individual, but usually in the 6 - 8 mos range.
I did mine at 6 months, while he was still with his dam. It was November, so the flies weren’t an issue.
I bred for me, and I don’t want/am not set up for/can’t afford a stallion - I just wanted a nice riding horse, so off they went.
I also like to geld mine while they are with their dam. Keeps them moving around and doesn’t really let them sulk. The ones I’ve had done healed extremely quickly and had their dams there to comfort them through the initial pain and discomfort.
The spring of their second year, before the flies. I know they can be done earlier, but that seems to be the best time for us for a few reasons.
