Hello ButtInTheDirt =]
while I am not an expert, I have worked with miniature horses for many years, and I will attempt to provide as much information as possible.
Miniature horses are generally 32"-38" tall (though many show-quality minatures are 28-30"), and are classified in two groups. Group A is generally show-sized miniatures, which stand anywhere less than 32" I believe, although dwarves can also be classified as group A. Group B is the larger, most often seen classification.
Miniatures come in any color, pattern, and shape that a normal horse would. Show minis are always bred to have the elegant, arab features of the arabian horse, while others have a stocky, pony-like stature.
They are small, but they act just like normal horses, needing the care, treatment, nutrition, exercise, and companionship that any full sized horse needs. They should not ever be ridden due to having characteristic weak backs, but are able to pull twice their weight easily. Most are very accepting and gentle, but on occasion you will find an indifferent or moody one, just as with any horse.
There are not really any special grooming precautions to take, but miniatures tend to have very thick, fuzzy coats for nearly half of the year and must be trimmed if you live in an area that is hot, as they do not handle heat very well. Their feet must always be taken care of and trimmed regularely to help prevent cushings disease, founder, and other feet problems.
Founder and colic are common illnesses that kill miniatures, because their digestive systems are extremely sensative. They must be given a proper diet with little forage (grass, if eaten at all, must be rationed and introduced slowly) and their sugar intake should be monitored closely. A miniature horse's organs are the same size as any full sized horses, meaning that they are all crammed into a small space. A small upset such as gas colic can be lethal. Alfalfa should be given mixed with another, less rich hay or not at all.
Fencing is always fun. They can get out of ANYTHING! We use four foot- three rail wooden fences with wire (small enough that their foot cannot get caught) stretched across the bottom two rails to prevent crawling out. (Yes, crawling.)
Dwarfism is the biggest genetic problem in miniature horses- a condition that can affect the horse's organs, appearance, abilities to function, airways, and lifespan (10-15 years is average for a minimal to average dwarf, and 4-7 years for a severe dwarf) for this reason, I recommend not ever breeding your own miniatures. Dwarfism is a painful disorder for horses, and can be avoided.
I personally love miniatures because of their 'pocket' size, ability to go just about anywhere, and affection.(well...maybe not the last part. My girl is quite oppinionated and would rather spend all of her time eating instead of working or playing with me!) they can do virtually anything a full sized horse can- whether it be jumping, lunging, obstacle, halter classes, or costume classes! Just remember that they take just as much time and training as any 1,000 lb animal ^^
Everyone in your life is meant to
be in your journey, but not all of
them are meant to stay till the end.