How to Help a Horse Gain or Lose Weight Safely

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-02

A horse that is not gaining weight usually needs more calories from forage and a properly balanced ration, not simply more grain. A horse that needs to lose weight needs fewer calories and more movement, plus a check for metabolic disease. Both directions start with the same first step, which is measuring body condition honestly instead of guessing from the stall door.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

• Score your horse's body condition and weigh or estimate his actual body weight before you change anything. You cannot track progress without a starting number.
• For weight gain, increase good-quality forage first. For most adult horses, forage should make up the majority of the ration, and feeding more than 50% of the ration dry matter as high-starch or high-sugar concentrates raises the risk of laminitis, colic, and equine gastric ulcer syndrome [1].
• Never feed more than 0.5% of body weight in grain-based concentrate at a single meal. For a 1,100-pound horse, that is about 5.5 pounds in one feeding [1].
• For weight loss, cut calories gradually and add exercise. A 10-week program combining feed restriction to 85% of digestible energy requirements with exercise five times per week produced measurable fat loss in overweight horses [2].
• Weight loss that happens without a diet change, or weight that will not come back despite good feeding, points to a medical problem and needs a veterinarian.

How to Tell If Your Horse Is Actually Thin or Fat

Body condition scoring is the tool that matters most. You assess fat cover over the neck, withers, shoulders, ribs, back, and tailhead, then assign a number. Most scoring systems run from 1 (emaciated) to 9 (obese), with 5 being ideal for many horses. Up to 70% of horses in domestic populations are overweight, so owners often underestimate fat cover [2].

Your hands do more work than your eyes. Press along the ribs. You should be able to feel them easily without pressing hard, and you should not see them sharply. Run your fingers over the crest of the neck and the area behind the shoulder. A hard, cresty neck is a warning sign, especially in ponies and easy keepers.

Take photos from the side and from behind on the same day each month. Fat shifts in specific places during weight loss, and a single overall score can hide changes in individual fat deposits [2]. Photos catch what your memory misses.

Weigh your horse if a scale is available at a barn, feed store, or clinic. If not, use a weight tape and stay consistent with the same tape and the same technique. A tape is not exact, but it tracks direction well.

Step-by-Step Plan for a Horse Not Gaining Weight

Rule Out Disease First

Before you add a single scoop of feed, have a veterinarian examine a thin horse. Dental disease, gastric ulcers, parasites, chronic pain, and kidney or liver problems all cause weight loss or poor weight gain. An 18-year-old horse with severe weight loss and muscle wasting turned out to have poor dentition, gastric ulcers, and other conditions, and his diet was also short on digestible energy, crude protein, lysine, threonine, vitamins, and minerals while being too high in sugar and starch [3]. Feeding alone would not have fixed him.

Ask your veterinarian about a fecal egg count, a dental exam, and baseline bloodwork. Treat what you find.

Fix the Forage Base

Forage comes first. Offer good-quality hay or pasture and let the horse eat as much as he can without becoming obese. If your horse is fed only dry hay, his water intake can almost double compared with a mixed hay and grain ration or pasture, so keep water clean and easy to reach [4]. Horses are often reluctant to put their heads into a trough below eye level, so keep the water level high [5].

If hay is poor quality or the horse cannot chew it well, soaked hay cubes, chopped forage, or beet pulp can help. Introduce any new feed slowly over 7 to 10 days.

Add Calories Without Overloading Starch

Once forage is maximized, add energy. Fat and highly digestible fiber sources are usually safer than large grain meals for a horse that needs to gain weight. If you do feed grain-based concentrate, split the daily amount into several small meals at least 4 hours apart, and keep any single meal under 0.5% of body weight [1].

A ration balancer or vitamin and mineral supplement fills the gaps that straight forage leaves behind. This matters most for horses on high-fiber, low-calorie diets, where a balancer supplies nutrients missing from the forage [1].

Feed the Old Horse Differently

Senior horses often need more than extra calories. Chewing problems, reduced digestion, and muscle loss all play a role. Soaked feeds, senior-specific complete feeds, and higher protein levels help maintain muscle. See Senior Horse Feeding and Nutrition for a fuller plan. The horse in the case report above was 18 and needed a balanced, energy- and protein-dense diet along with medical treatment [3].

Track Everything

Write down what you feed, how much, and when. Weigh feed with a scale instead of using scoops, because scoop weights vary wildly between products. Re-score body condition every two to four weeks and take photos.

Step-by-Step Plan for Helping a Horse Lose Weight

Cut Calories Slowly

Reduce forage and concentrate intake gradually. A study of overweight horses used a program that fed horses to 85% of their digestible energy requirements with no exercise, and a separate group got the same restriction plus exercise five times per week, over 10 weeks [2]. Both approaches produced fat loss, and the exercise group did better on some measures. Your veterinarian can help you set a target energy level for your horse.

Do not starve a horse. Severe restriction can cause problems, and horses need a minimum amount of forage to keep the gut working. Slow and steady wins here.

Add Exercise

Riding, lunging, or hand walking burns calories and builds muscle. Start with what your horse can handle and increase gradually. If your horse has laminitis, joint disease, or another condition, get veterinary clearance before you add work.

Watch for Metabolic Disease

Some horses gain weight on almost nothing. Equine metabolic syndrome is a common reason, and true hypothyroidism is rare in adult horses, so other causes for the signs should be considered first [6]. Supplements marketed for metabolic problems often lack scientific validation, and a randomized trial of ponies with equine metabolic syndrome tested a supplement containing leucine, resveratrol, and pyridoxine against a placebo [7]. Do not rely on a supplement to fix a metabolic problem. Ask your veterinarian about testing.

Keep the Gut Moving

Diet composition affects how the large intestine moves. In one study, horses fed a complete pelleted diet had a higher frequency of contractions at one part of the large colon than horses fed hay with a smaller amount of pelleted feed [8]. Fiber keeps the gut working normally, so keep forage in the diet even during weight loss.

Monthly Weight Management Schedule

Signs Something Is Wrong

Call your veterinarian if you see any of these:

• Weight loss despite a good appetite and a good ration
• Weight loss with a normal or increased appetite plus a pot belly, dull coat, or poor topline
• Diarrhea, colic, or difficulty chewing
• Muscle wasting along the back and hindquarters, especially in an older horse
• A hard, cresty neck, fat pads behind the shoulders or over the tailhead, or a horse that gains weight on very little feed
• Lethargy, poor performance, or a change in attitude
• Any horse that drops weight quickly over days instead of weeks

Common Mistakes Owners Make

Adding grain before checking teeth. A horse with painful teeth cannot chew hay well, so he drops weight no matter how much you feed. Fix the mouth first.

Feeding one huge grain meal. Large concentrate meals raise the risk of laminitis and digestive upset, and meals above 0.25% of body weight should not be offered at all [1]. Split feedings and space them at least 4 hours apart [1].

Ignoring water. A horse on dry hay drinks far more than one on pasture, and low water levels in a trough can make a horse refuse to drink [4][5]. Clean, full water is part of every weight plan.

Using a supplement instead of a diagnosis. Supplements for metabolic problems often lack proof, and a controlled trial in ponies with equine metabolic syndrome compared one such supplement against a placebo [7]. Testing beats guessing.

Changing the diet too fast. Sudden feed changes upset the gut. Transition over 7 to 10 days.

Forgetting the ration balancer. Horses on high-fiber, low-calorie diets can miss key nutrients, and a balancer fills those gaps [1].

Assuming a thin old horse is just old. Age alone does not explain weight loss. The 18-year-old horse in the case report had multiple treatable problems plus major dietary deficiencies [3].

Supplies and Setup That Matter

A digital scale for feed, a weight tape, a body condition score chart, and a notebook or phone app for records will do more for your horse than any single feed product. Keep a hay analysis on hand if you can get one, because it tells you what your forage actually provides.

For water, place troughs or buckets where your horse can reach in comfortably, and keep the level high [5]. In winter, check for ice. In summer, check for algae and refill often.

If your horse needs soaked feed, get a large tub and a routine. Soaking beet pulp or hay cubes takes time, and consistency matters more than speed.

For more on building a ration that fits your horse, see Feeding Horses: Forage, Grain, and Body Condition and Common Horse Feeding Mistakes to Avoid. If you also manage dogs, the same principles of measuring food and tracking body condition apply, as covered in Dog Weight Management: How to Help Your Dog Lose Weight Safely.

Limitations and When to Contact a Veterinarian

Home feeding changes work for simple cases, but they cannot fix disease. A horse with dental pain, ulcers, parasites, organ disease, or a metabolic disorder needs a diagnosis before any diet will help. Individual cases need a veterinarian, and no article can replace an exam.

Contact your veterinarian the same day if your horse stops eating, shows colic signs, has diarrhea, or drops weight rapidly over a few days.

Seek emergency care now if your horse is down and cannot rise, has severe abdominal pain, is sweating heavily with a distended abdomen, or shows signs of laminitis such as reluctance to move, a rocked-back stance, or heat in the hooves.

Schedule a routine visit if your horse is thin despite good feeding, is obese with a cresty neck or fat pads, has lost muscle along the back, or has not responded to a diet change after four to six weeks.

Frequently Asked Questions

How long does it take for a horse to gain weight?

Most horses show measurable change in four to eight weeks with a consistent, balanced ration. Older horses and those recovering from illness take longer. Recheck body condition every two to four weeks so you can adjust before progress stalls.

Should I feed more grain to help my horse gain weight?

Not as a first step. Increase good-quality forage and add fat or digestible fiber sources before you add starch. If you do feed grain, keep each meal small and split the daily amount across several feedings spaced at least four hours apart.

Can I let a thin horse eat as much hay as he wants?

Often yes, as long as the hay is good quality and the horse does not have a condition that requires restricted forage. Free-choice hay supports gut health and helps a thin horse gain. Your veterinarian can tell you whether your specific horse needs limits.

Why is my old horse losing weight even though he eats well?

Dental disease, reduced digestive efficiency, ulcers, and chronic illness are common reasons. An older horse may also need more protein and calories than he did when he was younger. A veterinary exam with bloodwork and a dental check is the right next step.

Can I use a supplement to help my horse lose weight?

Be careful. Many supplements sold for metabolic problems have not been scientifically validated, and one controlled trial tested a specific supplement against a placebo in ponies with equine metabolic syndrome. Diet, exercise, and veterinary testing do the real work. Ask your veterinarian before adding anything.

Related Articles

• Dog Weight Management: How to Help Your Dog Lose Weight Safely
• Feeding Horses: Forage, Grain, and Body Condition
• Dog Weight Loss Tips
• Senior Horse Feeding and Nutrition
• Common Horse Feeding Mistakes to Avoid
• Dog Not Eating: When to Worry and What to Do

References

1. Feeding Practices in Horses and Other Equids - Management and Nutrition. Merck Veterinary Manual.
2. Morphometric changes in overweight horses following 10-week weight loss programs. BMC veterinary research, 2025.
3. Successful nutritional management of a warmblood horse with multiple pathologies that respond to nutrition. Journal of equine veterinary science, 2026.
4. Nutritional Requirements of Horses and Other Equids - Management and Nutrition. Merck Veterinary Manual.
5. Nutrition of Horses - Management and Nutrition. Merck Veterinary Manual.
6. Thyroid Diseases. The Veterinary clinics of North America. Equine practice, 2026.
7. Leucine, pyridoxine and resveratrol supplementation alter metabolic parameters in ponies with equine metabolic syndrome. Equine veterinary journal, 2026.
8. Diet composition influences equine large intestinal motility as measured by transcutaneous ultrasound. American journal of veterinary research, 2026.

Further Reading

• Merck Veterinary Manual: Horse Owners