Ok, you knew I'd have to weigh in on this one, lol. Curlies are *my* breed after all, lol. I'm severely allergic to horses so they were a natural choice for me.
There are two types of curlies: dominant and recessive. The recessive show up in many breeds but mostly in foxtrotters and percherons. The foxtrotter recessive curlies usually are of very poor health and most are euthanized at birth. The recessive curly percherons are as healthy as any horse and usually are extremely curly. I think it's generally accepted that the recessive curlies are hypoallergenic as well. I've met a foxtrotter recessive but I didn't get close enough to tell if I was allergic or not.
The dominant gene curlies mostly originate from the mustang herds out west. There are still curlies among the blm herds. There was also a curly who showed up in the Ozarks of Missouri and was bred to alot of foxtrotters. There are dominant curlies who are registered foxtrotters. These seem to have a different type of gene from the ones that originated out west. I've personally tested both types of dominant curlies and I was allergic to neither.
There are also smooth coated curlies. These are horses from at least one curly parent. Alot of them are hypoallergenic for some people. The straights I've met I wasn't allergic to either.
There are two curly registries. One is the ABC which is a "blood" registry. This registry is for curlies who have two curly parents. The other registry is the ICHO. They will register any horse that has either a curly parent or a curly coat. That's a really simple explanation. There's alot of politics between the registries . . . There is also a curly sporthorse registry. This registry sponsors inspections where the horses are judged and rated as sport horses.
As to what they're good for . . . well that's a hard question. There are gaited curlies both of pure curly lines and outcrosses. They're suited for gaited horse things like trail riding and showing. There are curlies who are specifically bred to be sport horses. There are several breeders who outcross their curlies with warmbloods and tbs. One curly in particular was sucessful at upper level dressage. I just say upper level because I don't remember how far he went. 4th level maybe? I dunno. There are curlies who do western sports such as reining and roping. There are curly ponies of all sizes including ones that are 7/8ths mini. There are curlies who have been outcrossed with drafts and are nearly draft size. It seems that most people who show their curlies do so in the english disciplines. It's just easier to show a rare breed at open english shows. Alot of curlies are family horses for people with allergies. Most of us it seems, trail ride our curlies. There are curlies (some arab crosses) who do endurance as well.
Curlies tend to be very hardy. A couple of the original breeders started breeding them because the curly horses survived the harsh Montana winters that the other horses didn't. They usually have very hard, round hooves. Most curlies have short backs sometimes with the missing vertebrae. Curlies tend to be very friendly horses. They usually don't spook easy and their reaction to scary things is to turn and face it instead of running. Most curlies are easy to train. They can be like the appies in that their extreme intelligence can get in the way of training if you're using traditional methods. There have been misconceptions that curlies don't need things like grain, hoofcare or shelter. That's false, they're still horses and need the things regular horses do. Their coats are easily maintained. Some curlies will lose some or all of their manes and tails in the summer. Some curlies have super thick double manes.
Ok, here's my little herd. They are all outcrosses (mares were straights) and from homogygous for curls stallions. They are draft crosses. There's a pic of each of them in their summer coat and then the winter coat.
For more information visit
www.curlyhorsecountry.com. There are links to the registries, pics of curlies in their winter coats and other information.
If you have any other questions, just ask. I love my curlies and would be happy to talk more about them, lol.