Here are a few books you can look for if you want more information on having Miniature Horses. My all time favorite is tilted MINIATURE HORSES Their Care, Breeding and Coat Colors by Barbara Naviaux another one is THE BOOK OF MINIATURE HORSES Buying, Breeding, Training, Showing and Enjoying by Donna Campbell Smith. Also Miniature Horses A Veterinary Guide for Owners and Breeders by Rebecca L. Frankeny, VMD.
You can also check out the registries for more info. American Miniature Horse Association, http://www.amha.org/ American Miniature Horse Registry http://www.shetlandminiature.com/ and World Class Miniature Horse Registry http://www.wcmhr.com/
A few of the greatest things about Miniature Horses is that they don't take up as much room or they don't eat as much as the bigger horses do and guess what the clean up end isn't so much either. Minis are very inexpensive since they eat about 2-4 measuring cups of feed a day. A 50 lb. bag of top quality feed would last close to 50 days for 1 mini. But, of course you shouldn't have just one miniature horse because they are herd animals and would be much happier with a pal. One acre of pasture can sustain about five minis depending on the climate. During periods of time where you have no pasture grazing available you need to give a mini 1.5 - 2 pounds of good quality grass hay morning and night. A horse that is too fat is just as bad as one that is too thin. Check the ribs by gently pressing your fingers into the side. If you can't feel the ribs, slowly taper the grain and hay ration down, if grass is available you may need to limit it also. If the ribs are very easy to feel and are prominent, begin to slowly increase the amount of feed you give them. They should have a nice layer over their ribs. This test is especially important during the winter when minis have a heavier coat. They may "look" fine on weight, but do the rib test just to be sure.
Deworming: You will need to develop a deworming program for your Miniature Horse. ALL HORSES, BIG OR SMALL, ARE PRONE TO INTERNAL PARASITES!!! Theses parasites can severely affect your horse's general health and performance if left unchecked. It's important to have fecal eggs counts done on your horses a few times a year. It helps to see what kind of parasites your horse my have and to see how well your dewormer is working. You should also deworm you horse at least a couple times a year, like spring and fall for bots and tapeworms. Because bots don't show up in fecal egg counts and tapeworm eggs are hard to see. This way if fecal egg counts missed any parasites your horses would be safe too. We have found out that we have to deworm our horses more often than what the dewormer says in the spring and fall seasons. Also use caution when using Quest dewormer, I have heard if the dose isn't just right a Miniature Horse could die. If using a horse weight tape, please note that they are not very accurate for Miniature Horses.
Nutrition: It's important to understand the nutritional needs of Miniature Horses. Miniatures are prone to overeating and can develop problems from excessive food intake. Nutrition for Miniature Horses is similar to that for big horses but the differences in body size must always be considered. Miniature Horses will normally require a daily ration of grain and hay twice a day like morning and evening. Two feedings daily help the horse because of the size of their intestinal tract and the need for continual movement of food in their system. Plenty of clean water should always be available along with a salt block. Pasture access must be limited when grass is long and lush or founder (a painful and crippling condition) may result. As with all horses, feeding should be tailored to the individual animal.
Housing: Miniatures, though small, are hardy animals. They thrive on pasture, sunshine and room to run and play. If you are not planning to show your horse, a three sided run-in shed for protection from the cold winds and wet weather is usually sufficient shelter. Show horses are usually kept in individual stalls in a barn, but keep in mind they still need turn out time to run and play. MINIATURE HORSES STAND LOW TO THE GROUND, THEY ARE MORE AFFECTED BY AIRFLOW THAN THE LARGER HORSES. So the stalls should be built so the horses can look over the partitions and receive the benefits of airflow. An open airy barn is essential in maintaining good health for Miniature Horses.
Grooming: Whether your Miniature is a show horse, breeding stock, or companion, regular grooming is an essential aspect of his total care. Not only does the horse benefit from your grooming, he also becomes accustomed to your touch. This creates a special bond between you and your horse. When grooming always brush and comb with the hair, never against it. This will keep the coat soft and shinny and the mane and tail tangle free or at least the big tangles. During fly season the horse will appreciate a light covering of fly spray to help with all those nasty flies. While bathing is occasionally necessary and an important part of grooming it shouldn't be done to frequently as bathing removes much of the natural oils from the coat.
Hoof Care: Hooves should be picked out and trimmed for balance on a regular schedule.
Dental Care: Miniature Horses should have their teeth checked. It's easier to do routine dental care rather than wait until the teeth (and the problem) become challenges.
Veterinary Care: You and your veterinarian will want to establish a comprehensive health program for your Miniature. In gereral it's a good idea to have a vet who is familiar with your horse and his heath history so that the best possible care can be provided in case of an emergency situation.