I agree with AKPaintLover about the surrogate issue. If a person wants to have foals by a high-level competition mare, and don't want her to be off for a season, that's a very good answer. I'm all for it.
As for inducing heat cycles by light therapy or drugs... no, that's not right. Why mess with natural heat cycles? You're asking for trouble.
The lovely images above provided by CVLC Photography cvlphotography.com
It's putting a mare under lights that induces her to come into season earlier in the year. Mares stop having heats when they days are short and start having them again as the day gets longer. It's natures way of having them give birth during the time of year when the weather is milder and food is more plentiful.
But in situations where the horse isn't solely dependant on what food it can find in nature and has shelter provided, there is no reason why a horse shouldn't foal earlier in the year. It also makes more sense when horses are in situations where the rules that man has made to govern competition has horses counted as being born on Jan 1st no matter what the actual birthdate is. So you have horses being trained and competed on at 1.5 yrs because he is considered a 2 yr old.
I don't really understand how they can have more foals unless you are talking about the method tim referred to where they move the fetus to another mare. In that case, I could see why more heats would produce more foals, but the mare would not actually have to carry the foals to term.
It does seem a bit ridiculous to have to give them drugs for this purpose though. :)
Well thats what I heard, but this one guy is an arab breeder and he just never stops breeding his mares becuase he says if he does they won't be able to have any more foals. WTF?! So he breeds them from age 2 to death?. Those breeders are terrible. They breed there mare like 2 days after they had a foal and don't stop till there death.
It's just that not all mares will take exactly when you want them too.
Since most horse organizations make January 1 the birthday of all horses for show purposes, people like to get their mares to foal as close to January 1 as possible for obvious reasons. And since it's cold and dark in January and February and Mares have a roughly 11 month gestation period, people need to induce pregnancy when mares arent exactly in heat to get their foals as early as possible.