most horses do not need supplements as smrobs earlier stated. In fact, to many supplements can cause to high of protien levels which damage the kidney and liver. If your horse sweats and it looks like gillet foamy shave cream, you have overloaded your horses system . To many supplements can throw off the balance of minerals . Unless your horse has a specific problem , age, arthritis ,.Iron deficiency etc which are diagnosed by blood test, then you really only need forage (hay pasture ) free choice salt with minerals, and water lots of water :) and some shade or cover for rain. Your horse should be happy and healthy. Oh yes,, a clean pen and of course clean water.