The old song, 'mares eat oats, and does eat oats, and little lambs eat ivy' may be cute, but it's not entirely accurate. Mares, and all other horses need bulk in the form of hay or grass to make up the greater part of their diet. When flood, drought or other poor growing conditions hit, the hay crop can become scarce while the price goes up, up, up.
While you may be able to substitute oats, or other concentrates for part of your horse's diet, you'll still need to provide a substantial amount of digestible fiber. Hay Substitutes provides a list of feeds you can offer your horse when hay is hard to find.
Image: 2005 K. Blocksdorf
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