Are grapes good to give horses as a treat?

You can give horses small amounts of grapes as a treat, but because grapes are high in sugar, it is best to keep the quantity low. Horses rarely become iron deficient, and every horse feed already contains plenty of potassium. Horses produce their own B and K vitamins in the hindgut, so they do not need extra of either nutrient. That said, a couple of grapes as a treat works perfectly well.