One of the oldest management practices associated with horses is the weekly feeding of a hot bran mash and whilst offering your ponies a lovingly prepared bran mash may seem like a good way of rewarding them, it may be doing more harm than good. The main ingredient in a bran mash is wheat bran.  Wheat bran is a by-product of the manufacture of wheat; it consists of the outer fibrous layer of the wheat grain. Traditionally when horses were used for farm work a bran mash was offered on a Saturday night, the eve of their rest day.  It was thought that bran mashes had a laxative effect that would “clean them out” and help prevent colic.  Although horses aren’t used for farm work today many still receive a weekly bran mash for the same reasons. Research has shown that bran does not have a laxative effect.  Studies have found that adding wheat bran to the diet did not soften the stools.  Many attributed the laxative effect to the fibre in the wheat bran however what bran is not a high fibre feed and should be thought of as a grain, rather than forage. However, all bran’s are very high in phosphorus having en extremely lopsided calcium: phosphorous ration of 1: 12, so if you feed bran every day this balance must be addressed. The ideal ratio of calcium to phosphorus in a horses diet is 1: 1 or 1: 2 so if you are feeding bran daily you will need to balance the mineral content of your horses diet either with a mineral supplement of with a feed naturally high in calcium. This is as the two most abundant bodily minerals, calcium and phosphorus work together to build sound bones and assist muscle function but to do this they must be absorbed in appropriate proportions by the body.  So when a horse ingests phosphorus he must also ingest an equal or slightly greater amount of calcium.  If there is not enough calcium to match the phosphorus in a bran fed horses daily diet extra calcium will be pulled from the horses bones in order to balance the excess phosphorus in his gut.  If a horse gets too much phosphorus over a long period of time, his body will take so much calcium from the bones that it weakens the skeleton. Experienced equestrians know that any changes to the horses diet must be made gradually but despite this some people will feed a bran mash once a week.  Although this will not overly affect mineral imbalances, it will instead be upsetting the microorganisms in the digestive tract that aid digestion.  This usually results in diarrhea, which could be another reason why bran mash was once thought of as being a laxative.