There have been several methods devised for developing feed rations for horses. Most methods are based upon a trial and error basis, making substitutions until all factors balance in the ration. Many people do not care to make their own ration, preferring to buy commercial mixes.
Mixes made by respectable feed manufacturers are very good.
If you are feeding only a few horses or do not want the hassle of always having to check the nutrient levels of your feed, commercial mixes are a good way to meet the needs of the horse. However, you need to know which commercial mix to buy to match the feeds that you may already be feeding. If you are raising foals, you may want to also add 15 lb. of brewers dried yeast per ton of creep ration to provide B vitamins. Table 7 lists the vitamin requirements for horses. Grains are high in phosphorus, low in calcium.