It does not make sense at first. Your horse cleans up every meal, never leaves a scrap, and yet the ribs are starting to show. Eating well but losing weight is a real and common puzzle, and the good news is the list of causes is fairly short.
When intake looks fine but condition slips, the problem is usually one of three things: the horse cannot chew the feed well, cannot absorb it well, or is burning more than it takes in. Let's walk through the usual culprits.
Cause 1: Teeth
This is the first thing to check. A horse can act hungry and still chew poorly. Sharp points, hooks, and worn or missing teeth all reduce chewing. Poorly chewed feed passes through without giving up its full value. Look for dropped, balled-up feed (called quidding), slow eating, or whole grains in the manure. A dental exam is the fix.
Cause 2: Parasites
Worms quietly steal nutrition and damage the gut wall, so a horse can eat normally and still lose ground. Work with your vet on a fecal egg count and a targeted deworming plan rather than guessing.
Cause 3: Poor absorption
Sometimes the gut itself is not pulling nutrients out of the feed. This can follow parasite damage, inflammation, or other gut problems. The horse eats, but less of the meal makes it into the body. This is a vet workup, not a feed swap.
Cause 4: Ulcers and discomfort
Stomach ulcers are common, especially in horses in work or under stress. A horse with ulcers may still eat but lose condition, act girthy, or seem off. Your vet can advise on diagnosis and treatment.
Cause 5: Poor forage quality
Quantity is not the same as quality. A horse can eat a full hay net of low-quality, stemmy, or old hay and still fall short on calories and protein. If the hay is poor, more of it may not be enough. A forage test or better hay can change the picture quickly.
Cause 6: Feed efficiency and mineral balance
Minerals help the body use the feed it gets. When trace minerals are low or out of balance, the diet on paper may not perform as well in the horse. This is rarely the only cause of weight loss, but it can be part of why a good ration is underperforming. It is also something you can screen for.
Ration looks fine but the weight keeps slipping? Order a hair mineral analysis test kit to rule the mineral side in or out.
When to call your vet
Bring in your veterinarian promptly if you see:
- Fast or steady weight loss despite a full appetite
- Diarrhea, colic signs, or fever
- Quidding or trouble chewing
- An older horse losing condition over weeks
Steady weight loss with a good appetite can point to gut or other internal problems that need a workup, so do not wait too long to ask.
A simple order to check things
- Book a dental exam. Rule out chewing problems first.
- Run a fecal egg count. Then deworm based on the result.
- Upgrade the forage. Test the hay or switch to better quality.
- Screen minerals and metals. Use a hair sample to check the nutrition side.
- See your vet if weight keeps dropping or red flags appear.
Sand and gut health
Here is one cause owners often miss. Horses on sandy ground can take in sand as they graze. Over time, sand sits in the gut. It can irritate the gut and lower how well feed is absorbed.
Signs can be loose manure or mild colic. Ask your vet about sand and the safest way to manage it. Feeding hay off the ground can help reduce how much sand a horse takes in.
How to add calories safely
Once you find the cause, you may need to rebuild weight. Do it slowly. Fast refeeding can be risky, so go gradual.
- Start with more forage. Better hay, or more of it, is the safest first step.
- Add fat for calories. A fat source like oil or ground flax adds energy without a lot of sugar.
- Split meals. Smaller, more frequent meals are easier on the gut.
- Track it. Use a weight tape and photos every couple of weeks.
If your horse is very thin, plan the refeeding with your vet. Slow and steady wins here.
Ulcers: a closer look
Stomach ulcers deserve their own note. They are common, especially in horses in work or under stress. And a horse with ulcers can still eat while losing condition.
Watch for signs like a girthy reaction, picky eating, a dull mood, or weight loss with a good appetite. Stress, hard work, and long gaps between meals all raise the risk. Your vet can confirm ulcers and guide treatment. Steady forage and fewer empty-stomach hours can help lower the risk.
Test your hay
One step pays off fast: test your forage. A hay test shows the real calories and protein in what you feed. Many owners find their hay is weaker than it looks. Better hay, or more of it, can turn the weight around without any fancy products. Ask your local extension office or feed supplier how to get a hay sample tested.
Common questions
Why is my horse losing weight but still eating?
The most common reasons are dental problems, parasites, poor absorption, ulcers, and low-quality forage. Mineral balance can also reduce how well the diet performs. A vet exam plus a hair mineral screen helps narrow it down.
Could it be his teeth even if he eats fast?
Yes. A horse can be eager to eat and still chew poorly. Watch for quidding and whole grain in the manure, and book a dental exam.
Will a mineral test tell me why?
It screens the mineral and heavy-metal side and gives a baseline to track. It is a screening tool, not a diagnosis, so use it alongside your vet's exam.
Eating well but losing weight almost always traces back to chewing, absorbing, or feed quality. Work through the list, and screen the nutrition side so nothing is missed. Order a hair mineral analysis test kit, and see the complete guide to weight loss in horses for the full picture.
Sources:
Merck Veterinary Manual. Nutritional Diseases of Horses and Other Equids: https://www.merckvetmanual.com/management-and-nutrition/nutrition-horses/nutritional-diseases-of-horses-and-other-equids
van der Merwe D, et al. Evaluation of hair analysis for trace mineral status and toxic heavy metals in horses in the Netherlands. J Vet Diagn Invest. 2022 (PMC9597333): https://pmc.ncbi.nlm.nih.gov/articles/PMC9597333/
Merck Veterinary Manual. Clinical Signs of Pituitary Pars Intermedia Dysfunction: https://www.merckvetmanual.com/multimedia/table/clinical-signs-of-pituitary-pars-intermedia-dysfunction
Merck Veterinary Manual. Nutritional Requirements of Horses and Other Equids: https://www.merckvetmanual.com/management-and-nutrition/nutrition-horses/nutritional-requirements-of-horses-and-other-equids