By Juliet M. Getty, Ph.D. - “For an adult horse with moderate activity, feed .75 to 1.0 pounds per 100 pounds of body weight.” These are the feeding instructions for a popular commercially fortified feed. If your horse weighs 1100 pounds (500 kilograms), you’ll need to feed 8.25 to 11 pounds of feed per day to ensure he’s receiving enough calories, protein, vitamins, and minerals. That’s a lot of feed!