The Best Feeds for Helping a Horse Gain Weight
hays are higher in protein and some minerals such as calcium. Giving these types of hays to an underweight horse may be needed. Go slowly when introducing any new feed to your horse even if it is "only hay."
Extra Feeds for Skinny Horses
Beet pulp is often fed as a supplement because it is high in fiber, which the horse can turn into energy.2 Some people prefer to give their horses pelleted feed because they feel this is more easily digestible. Older horses might be able to digest "cooked" grains easier than regular grains, so a specially prepared senior feed might be helpful. For horses with bad teeth, smaller pellets or grains are easier to chew than larger pellets or cubes. Rice bran and flax are also popular additions to the diets of underweight horses
Oils such as bran, rice, corn, flax, and other grain oils are often used to boost the energy and calories of a horse’s feed. Some people feel they also help keep the horse’s skin healthy and coat shining. Go carefully when adding these oils to your horse’s diet; too much oil in the diet can cause diarrhea.3
Whenever you are changing the number of concentrates, do it gradually to decrease the possibility of problems like founder or colic. Also use a weight tape to get an estimate on your horse's body weight. Repeat the weight tape two weeks after you've made a diet change. Record these numbers and measure your horse's weight regularly. If you don't see the changes you expect, talk to your veterinarian and/or equine nutritionist