Taking in a horse that is malnourished, or having a horse that is difficult to keep weight on, can be a challenge. You want the horse to gain weight, yet overfeeding can cause all kinds of problems, such as colic and founder. Knowing how to put weight on your skinny horse in a safe manner is important.
Feed top quality alfalfa to your horse twice a day. Start with one flake mixed with coastal hay, or dried bermudagrass. Work up to two flakes twice a day. Do this gradually over a period of two weeks to a month to avoid colic. Alfalfa is one of the best possible feeds for a thin horse, adding a whopping 300 calories per pound of hay.
Add fat to your horse's diet. This can most safely be done by adding up to one cup of corn or vegetable oil to your horse's feed per day. This works best with a sweet feed, as horses may not like the oily taste if it is added to plain oats or other grain.
Feed a high-fat concentrate. These are feeds designed with a higher fat content. Feeds with six to eight per cent fat are excellent for putting weight on thin horses. Most "senior" horse feeds have a higher fat content and are easier to chew and digest, which makes them ideal for thin horses.
Add probiotics to your horse's feed. Adding these beneficial microbials to the gut can maximise digestion, which will aid in nutrient and calorie absorbtion. You can purchase these at any feed store.
Feed free choice high-quality coastal hay. This means that the horse can eat as much and as often as it likes. Getting a healthy gut requires lots of fibre for a horse in poor condition and constant ingestion of lower protein hay, in addition to the other feeds such as alfalfa and concentrates, will guarantee a gradual and healthy return to a good weight.
Keeping the thin horse separate from other horses until it gains weight will help make sure that the extra feed is given only to the horse that needs it.
Do not make sudden changes to any horse's diet. If you shock a skinny horse with a mass of fat and protein, you are quite likely to kill it with colic or founder.