I am probably guilty of using "minimal" to describe some minis that show signs of dwarfism, but may in fact be arbitrary to many others.
For example, I had a little mare born here that had what I consider signs of dwarfism, though she was also quite sound and for the most part, as correct in the leg angulation as many horses being routinely bred.
Other than a straight hind leg angle, she really didn't show a lot of sign outwardly of being a non-breeding prospect.
What added up for me w/this mare:
Overall large bone density for her height of 30". A high dome on her forehead (not between the eyes but higher between the ears and eyes). An underbite caused by crowding (most likely the way her skull was made was why she had the dome and the underbite/dental crowding) which was NOT anything other than congenital.
These things added up to me to a "clue" as to what may have been hiding genetically. Looking at her dam, I think that is where it came from, as she showed the same problems though her underbite resolved itself as she grew and as a five year old mare it was perfectly straight and normal. The sire showed NO signs.
It is no ONE thing that says "dwarf" and it's not type vs. type.
What it is is a series of outward clues (when we can see them) and then again, it may be that the ones that have not even one sign may in fact be hiding so that when bred with one that may exhibit a "mild" sign of dwarfism, we get a severely afflicted dwarf, one of those that you look at and go right away, "dwarf".
I hate to say it, but in a lot of cases when someone is brave enough to post pics of sire and dam, it is somewhat apparent where things went wrong. I'm not saying I can predict or know, but in some cases it's fairly easy to see where the genes added up to a severe expression of the disorder.
Before I ever got into minis I went over to look at a herd of horses that a lady near here had for sale. I was drawn off the road by the color at first. As I got closer, even though I had had somewhat limited experience with minis, I could see that 90% of the herd was almost grotesquely malformed in one respect or the other. They were all closely or distantly related. One horse was the most beautiful liver color with yellow eyes. He had such a severe underbite that his tongue would not fit in his mouth. It was blistered and dried and looked miserable. Other than that, his legs and his shape was fine. Proportions were great. He DID have heavy, thick bones, and he was 35" tall, too. His full brother, however, was a black blanket appaloosa approx. 25" tall w/severe afflictions; huge pot belly, large, domed head and crooked legs.
The main criteria for me as I look at a horse are:
Overall proportions, i.e., nothing severely out of proportion with the rest (not talking a slightly big head, or a bit short legged, but glaringly off).
Under that proportion comparison goes the bone size for the height/proportion. I want to stress that I'm not talking "draft vs. qh vs. arab" in "TYPE" this is not about type. Many of the older dwarf types were advertised as being "arabian" type due to the bulge on the head, but in fact, if you look, their bones were HUGE for their heights.
Under or over bite. these may exist on their own in any number of horses and while to me they are a reason to keep them out of the breeding shed, when combined with any of the other things on "my" list, they start to hint dwarf. BUT, this affliction does exist, IMO, in horses that aren't necessarily anything close to a dwarf, and it may be a problem of dental care rather than congenital. A good equine dentist can confirm or help repair the issue if it's not truly congenital (i.e. passed onto other generations due to the way the head is formed).
Crooked legs. Again this problem happens in any number of horses in any population. In Miniature Horses, I believe it's more of a problem due to unwise breeding practices or just overlooking correctness for whatever trait that was desirable at the time. A bit of cowhockedness does not make a dwarf. Nor does a horse who might be over at the knees. What would be a bit more concerning to me would be of course something severe or something afflicting just one leg (such as knuckling over or to either side, or problems with the way the bones are made). Depending on severity, it may be that this one thing is enough to determine dwarfism and for sure the unsuitability for breeding. Many dwarfs are congenitally flawed with missing or extra joints, tendon issues and the like. It can either be a death sentence for them, or a severe pain and management issue. Sometimes it CAN be managed.
A pot belly that is not related to anything medical (i.e. worms, pregnancy, etc.).
Misplaced dome on the head. A high bulge that does not even out or look proportionate or natural as the horse grows. Tends to go with the characteristic of high, oddly-placed nostrils (and I see a lot of underbites w/this "look" too).
I don't know what others' "criteria" are, but these are some of the things I look for and sort of check off and note. Combine any or all of these and of course some of them should be "no breed" designations anyway, but even in their mild form, they just tell me to look elsewhere for breeding stock and/or find another use/enjoyment for that horse.
I have permission from Goldie's owner to use her picture for comparison and I will post it here, for educational purposes:
Maybe a lot of people can't see it, but she does have a dome high up closer to her ears than is reasonable (can also sort of see her underbite from the outside, here). She was preparing to go in Color class at the time. She LOVED showing and being handled/played with.
Yearling. Again, maybe it's not easy to see, but the outward signs as well as her underbite said possible dwarf to me. She also tended to grow upright hooves, so I would say was mildly clubfooted and we had to make sure to correct it with each trim.
She did outgrow the "butt high" but she still has a very straight hind leg angle, overall heavy bone for her height, and the odd shape/crowding of skull/jaw/dental arcade confirmed by an equine dentist. Her teeth were so crowded by the shape of her head that her wolf teeth grew behind her two front incisors. Nothing we did could change the underbite as it was from the shape and crowding, but it was manageable and she didn't have a lot of trouble eating.
She is now a beloved pet.
Liz M.
