Eating like a horse, facts confirm, is a bit of an anti-truth. Horses actually have very small stomachs for their size, and they can't regurgitate or chew cud like cows do. The horse has a one-way digestive system, so if he eats something he shouldn't have, you'll have to wait until it goes through his whole digestive tract to work its way out.
Horses who eat too much grain can colic, which is a stomach-ache and then some. Colic can kill a horse unless it is caught and treated early enough. Treatment includes keeping the horse quiet, not allowing him to roll, and assisting the vet in administering pain medication and then trying to keep the horse calm until the stomach upset passes.
For this reason among many, you must be careful what you feed horses. Grass hay is pretty hard to mess up with - as long as it has good color, is not hot and has no foreign objects in it, a horse can eat as much grass hay as he wishes. Alfalfa hay is richer, and you should wean a horse onto it gradually. Timothy hay is another tasty hay that most horses like. Each individual horse, facts say, has a diet that will work best for him.
Most horses who do any work at all are also fed grain or a complete pelleted feed. Oats are still used in sweet feed mixes, and these are useful for picky eaters. Most other horses do fine on a pelleted feed which is based on hay, and has a good deal of roughage in it. That's not to say that you should only feed your horse grain. He should be fed much more hay than grain. It's not uncommon for a fully grown 16 hand horse to get just a small coffee can of sweet feed twice a day, but free choice hay at all other times.
If you need to change the type of food your horse eats, it must be done gradually. Add a little more new feed to a little less old food every day until he is switched over. This helps to keep his stomach from getting upset.
Horses play like horses, so have a first aid kit handy in your tack room or barn. Most injuries will just be small cuts or bumps, but a well-placed kick can break a leg of a stablemate if they're playing rough out in the pasture.
Have the telephone and cell numbers for your vet posted in the barn, and use them if you need them. A vet call is not cheap, and an emergency call costs even more, but if a responsible owner or barn staff thinks he is needed, make the call. You don't want to try to take care of a wound that's beyond your ability to care for. If a wound is deep or open, the vet will stitch it up, and return in ten days to remove the sutures. He will also give your horse a tetanus booster and some pain meds and anti-inflammatories. Some of these are shots and some are oral medications. It's good to always have someone at the barn who can give shots and administer medications.
There is nothing quite like watching a horse at liberty in a large pasture, running free like he was intended to when he was created.