One cause of impaction can be dehydration. Horses need constant water; even being without water for an hour or so can cause problems. Making sure it is fresh is important, because horses may ignore water that isn't as fresh as they'd like it to be. Dental health is important for maintaining healthy horses. Good teeth encourage your horse to chew properly, which makes an impaction less likely. Horses need roughage to make sure food moves through their system as it should. Therefore, ensure your horse has fresh hay available or is allowed to graze in a pasture every day. If you give your horse food on the ground, your horse may accidentally eat other things that are not food. If your horse eats enough of these other particles, it can block his bowels. For instance, your horse may eat too much sand with the hay, causing problems. Regular exercise keeps your horse in a routine and can also move the bowels along. Make sure to encourage exercise at least once a day. You provide some de-wormers daily, while others require you to give them less often; your vet can help you determine the best kind for your horses. This process helps control parasites, and an excess of parasites can sometimes lead to colic in horses. Ask your veterinarian about de-worming foals, as they may require special treatment.

Summary:
Provide plenty of fresh water. Schedule regular dental care. Give your horse enough roughage. Provide food in troughs. Exercise your horse regularly. De-worm on a regular basis.