There are a lot of breeders here who breed on foal heat (first heat), I prefer not to for many reasons, none of them having to do with humanizing (that's a real word but we use anthropomorphizing more often) the horse . I prefer to allow the mare to raise her foal to weaning, then after the foal is weaned, I like to put the foal back with the mare for the next 6 months or so. Before weaning, I put mare and foal out with other horses, then pull the mare after the foal is comfortable with the other mares and has chosen an 'auntie' or gelding 'uncle'. After a couple of months, once the mare has stopped lactating, I put her back in the group and let them all go on together until the mare has had a full year off. When I was breeding more mares for myself, I bred each one every other year, so they would have plenty of time off to get healed up and healthy. Now that I'm not breeding but 1 or 2 foals each year, and my mares are getting older, I have one who needs to be bred each year or she'll soon not be able to conceive. I have had most of my mares since they were very young mares, and I keep them until they're old and pass of old age. As I'm getting older, I'm breeding less and not wanting to breed as often, so my oldest and best mare may be allowed to go barren in a couple of years.So, where I live almost every mare is a breeding machine. They have their foal and in the first heat after that, they breed them again. For me, that's not ethic at all, but I guess if the horse was "free" they would reproduce every year... I see my neighbours breeding their mare every single year and I kind of hate it haha (but maybe I'm humanizing this?? -- is humanizing a word in english?).
I'm not talking about high competition or performance horse, but just horses used for trail riding and light work (we don't have many horse breeds here or purebreds). Here with high competition horses they take the mare's egg, fertilized in vitro and the result is implanted in a receptor mare (or they make a natural mount, then take the embryo and implant it in a receptor mare) that's used for gestation and upbringing.
We, as a nation, do quite a bit of ET (embryo transfer) and leasing out recip mares is actually a pretty good industry for some folks.
Ideally the horses should be well bred, well conformed, proven in some kind of discipline, and really good natured. Not everyone subscribes to those particular ideals. Many people breed 'paper to paper' just looking at pedigrees and not looking at the mare in front of them and looking for a stallion to strengthen the strong points and make up for any weak points. Too many breed ill tempered animals because they're bred to death or superb performance animals, but you can't trust them for a minute.