A substance or medication that increases bowel movement and relieves constipation. In horses laxative medication can be administered to relieve impaction colics. There are also some feed stuffs which are believed to have laxative effects (e.g. bran mash, oil), although there is little supporting research. Laxatives should not be given without consulting a veterinarian, as with certain types of colic the administration of laxatives can actually worsen the situation.