Are you worried because your horse is getting thinner and thinner despite being fed enough, and its ribs are clearly visible? Weight loss in horses can have many causes – from dental problems to serious internal diseases. It is crucial to systematically search for the cause. In this guide, you will learn how to proceed step by step, which examinations are important, and how you can help your horse regain a healthy weight.

When is a horse too thin?

Not every lean horse is automatically too thin. The Body Condition Score (BCS) is a standardized method for assessing body condition. 

The scale ranges from 1 (extremely thin) to 9 (extremely obese).

• BCS 1 – Extremely emaciated:
  • Bones from the ribs, shoulder, hip, and back protrude significantly.
  • No palpable fat deposits 
• BCS 2-3 – Very thin:
  • Ribs, shoulder blades, and hip bones clearly visible
  • Minimal fat coverage 
• BCS 4-5 – Ideal:
  • Ribs are easy to feel but not visible. 
  • Even fat coverage
• BCS 6-7 – Overweight:
  • Ribs difficult to feel 
  • Significant fat deposits
• BCS 8-9 – Obese:
  • Ribs not palpable 
  • Pronounced fat deposits all over the body

How would you assess their nutritional status?

• Ribs: Should be easy to feel but not protrude
• Back: The spine should not protrude.
• Croup: The hip bones should not protrude significantly.
• Shoulders: Shoulder blades should not protrude sharply.
• Neck: Horses that are too thin often have sunken necks, while horses that are too fat often have noticeable fat deposits on the crest of the mane.

The most common causes of weight loss in horses

1. Insufficient feed intake or increased energy requirements

The horse is not getting enough feed overall. This may be due to poor feed quality or feed with low nutritional value. Lower-ranking horses may be driven away from the feed by others, and stress caused by poor herd dynamics or suboptimal husbandry conditions can also affect feed intake. Another possible cause of weight loss can be intensive training or unusual physical exertion without a corresponding adjustment in feed. Pregnant or lactating mares also have increased energy requirements. During the coat change, especially in spring and fall, horses need additional energy, especially older horses or horses with underlying conditions such as metabolic problems. Older horses with poor feed conversion generally have increased energy requirements.

2. Dental problems:

Dental problems are a common cause of weight loss in horses. Sharp edges, missing teeth, or gum inflammation prevent effective chewing. The horse eats food but cannot chew it properly and digest it.

3. Parasite infestation

Severe worm infestation is a common cause of weight loss. Worms in the intestines deprive the body of nutrients, which is particularly relevant in cases of severe infestation due to inadequate deworming. In addition to weight loss, parasite infestation can also lead to colic and diarrhea. Young horses are particularly prone to severe worm infestation.

4. Gastrointestinal disorders

Various diseases of the gastrointestinal tract can lead to weight loss. Stomach ulcers cause pain and loss of appetite, leading to reduced food intake. Chronic intestinal inflammation impairs the absorption of nutrients. Sand accumulations in the intestine can trigger colic and reduce nutrient absorption.

5. Chronic diseases or infections:

Metabolic disorders such as equine Cushing's syndrome (medically known as pituitary pars intermedia dysfunction (PPID)) can lead to muscle wasting and weight loss. Chronic liver or kidney disease can also be a possible cause of weight loss. In cases of chronic inflammation, the body uses a lot of energy for immune defense and thus loses nutrients. 

6. Tumor diseases:

Tumors are a possible cause of weight loss, especially in older horses. Lymphomas and tumors in the abdominal cavity are often difficult to diagnose in horses, but can severely impair the horse's general well-being. Tumors can also lead to colic, changes in blood count, and other physical symptoms such as edema.

Is your horse losing weight and you can't find the cause? The specialists at Altano clinics carry out comprehensive diagnostics. Find a clinic near you now.

The diagnostic step-by-step plan: How to proceed systematically

If your horse is too thin, you should work through these steps one by one:

Step 1: Basic check by the horse owner

Check the amount of feed: Weigh the feed! Horses need at least 1.5 to 2 kg of hay per 100 kg of body weight per day. A horse weighing 500 kg therefore needs 7.5 to 10 kg of hay per day – plus concentrated feed as required. Weigh your horse if you are unsure of its weight. This allows weight loss to be documented objectively.

Assess feed quality: Is the hay moldy, dusty, or of poor quality? Smell it—good hay smells aromatic and is greenish in color.

Observe eating habits: Does the horse eat slowly or leave food behind? Is it being chased away by other horses? Signs of dental problems: The horse rolls hay (forms hay balls in its mouth and spits them out). You may notice one-sided chewing or head tilting while eating. An unpleasant smell from the mouth, increased salivation, or resistance to the bit when riding can also indicate dental problems.

Check the consistency of the feces: Are whole hay fibers or grains of cereal visible in the feces? This may be an indication of poor digestion or dental problems.

Stage 2: Basic veterinary examination

Medical history: Tell your veterinarian about your horse's symptoms. Anything you have noticed may be relevant. Document how long the horse has been losing weight and whether there are any other known problems or illnesses.

General clinical examination: This is the very first veterinary examination. The horse is thoroughly examined for any clinical abnormalities. Among other things, heart rate, respiratory rate, and temperature are determined.  

Depending on what your veterinarian finds during the general examination, further steps will be taken and additional tests will be carried out. It is not always possible to carry out all tests at the home stable; under certain circumstances, a referral to an equine clinic for further diagnosis may be necessary.

Dental check-up: This is an important step! Have your horse's teeth thoroughly examined and treated if necessary. Even minor dental problems can have major consequences. A common dental problem is sharp edges on the molars, which are caused by uneven wear. Missing teeth can cause problems, especially in older horses. EOTRH (Equine Odontoclastic Tooth Resorption and Hypercementosis) is a painful disease of the incisors that occurs mainly in older horses. To prevent weight loss due to dental problems, dental checkups should be performed by a veterinarian at least once a year, and twice a year for older horses.

Fecal examination: A parasitological examination of the feces is performed to rule out a parasite infestation. If suspected, this examination can be repeated after 2 weeks.

Stage 3: Laboratory diagnostics

If the initial examination does not reveal a clear cause, laboratory tests can provide further clues. The first step is a blood test, and further tests may be necessary following specific diagnostics. Sometimes a complete blood count can already provide clues as to the cause of the weight loss. In addition, specific diseases such as Cushing's (PPID) can be diagnosed by means of a blood test. A red blood count and the determination of serum amyloid A levels can provide indications of acute inflammation.

Stage 4: Further diagnostics

If the cause still cannot be found, it usually makes sense to take the horse to a clinic for a detailed examination of the problem. Various tests may be necessary, for example:

• Gastroscopy:Gastric ulcers (EGUS) can lead to poor feed intake and weight loss.
• Abdominal ultrasound: Assessment of the liver, kidneys, spleen, and intestines can provide important information. If there is free fluid in the abdominal cavity, it may be necessary to perform a puncture. 
• Rectal examination: Palpation of the internal organs from the rectum is part of the standard examination. This also allows the consistency, quantity, and odor of the feces to be assessed.
• X-ray or other imaging techniques:Sand deposits in the large intestine can be diagnosed using X-ray imaging.
• Abdominal puncture: Free fluid from the abdomen can be examined in the laboratory after a puncture. This can provide indications of intestinal disease or a tumor.
• Glucose absorption test: This test checks whether the intestinal wall absorbs nutrients normally or whether there is a problem there.

Feeding optimization: How to help your horse gain weight

Once the cause has been identified and treated, it is time to optimize feeding:

Basic principle: roughage, roughage, roughage!

Increase the amount of hay to 2 to 2.5 percent of body weight. If your horse has dental problems, soaked hay cobs can be used as an alternative. Feed several small portions throughout the day. Choose high-quality, energy-rich hay.

Targeted use of concentrated feed:

Choose a high-quality, easily digestible concentrated feed. Grains provide quick energy, but should be used in moderation. Oils (linseed oil, rice germ oil) are energy-rich supplements – 50-100 ml can be fed daily. The amount of oil can be increased, but horses need to get used to it slowly. Alfalfa (as cobs or chaff) is rich in protein and energy. Mash is easily digestible and can be fed as a supplement.

Special feed for underweight horses:

There are commercial feed supplements with high energy density. These often contain oils, alfalfa, and easily digestible fibers. The use of such special feed can be particularly beneficial for older horses or horses recovering from illness.

Additives for support:

• Probiotics support the intestinal flora
• Brewer's yeast promotes appetite and digestion  
• Mineral feed should always be fed in sufficient quantities to meet requirements.

Important: Increase the amount of food slowly! Abrupt changes can lead to colic or diarrhea. Increase the amount gradually over 2 to 3 weeks.

Would you like personalized feeding advice for your horse? The experts at the Altano Group will be happy to help you. Make an appointment.

Special challenges: Older horses

Why do older horses gain weight more easily?

Older horses often have poorer digestive performance—their intestines no longer work as efficiently. The horse eats enough, but absorbs nutrients less effectively. Dental problems are also more common, which reduces energy intake even though the horse appears to be eating well. Reduced appetite can be another reason. Age-related metabolic changes (especially Cushing's disease) lead to muscle loss, fat redistribution, and poorer feed utilization. Muscle loss makes the horse appear thinner, even if its appetite is normal. Age-related organ problems, such as liver disease or kidney failure, mean that energy cannot be utilized as effectively.

Solutions for seniors:

Soaked hay cobs or pelletized hay are easier to chew and should therefore be offered as a supplement. High-energy senior feed can help to meet the horse's calorie requirements if it has a poor appetite. Several small meals spread throughout the day provide constant stimulation and increase feed intake. Regular dental check-ups (twice a year) should be standard for older horses. Underlying diseases in horses must be treated consistently. For example, if PPID (Cushing's) is diagnosed, long-term medication with Prascend is necessary. Supplementing feed with amino acids to maintain muscle mass can help reduce age-related muscle loss.

Would you like personalized feeding advice for your older horse? The experts at the Altano Group will be happy to help you. Make an appointment.

How quickly should a horse gain weight?

Patience is required! Gaining weight too quickly can be harmful.

Realistic pace:

A healthy horse should gain approximately 0.5 to 1 kg per week. This corresponds to approximately 2 to 4 kg per month. It takes approximately 6 to 12 weeks to increase one BCS point. If an underlying condition has been successfully treated, weight gain may occur more quickly in some circumstances.

Monitor progress:

Weigh your horse regularly (horse scale or weight tape). Take a photo of the horse every 2 weeks from the same perspective. Assess the BCS monthly. Adjust the amount of feed as needed.

Warning signs:

If the horse does not gain weight despite optimized feeding, something is wrong. Look for the cause again. Have further tests carried out.

Common mistakes when gaining weight

Avoid these common mistakes:

Mistake 1: Too much concentrated feed at once: This can lead to digestive problems, colic, or laminitis. Better: Several small portions.

Mistake 2: Neglecting roughage: Concentrated feed alone does not provide sufficient nutrition and health. The basis must always be sufficient roughage.

Mistake 3: Changing food too quickly: The digestive tract needs time to adjust. Change the food gradually over 2-3 weeks.

Mistake 4: Not identifying the cause: If you simply feed the horse more without treating the underlying condition, it will not gain weight.

Mistake 5: Impatience: Gaining weight takes time. Don't expect miracles within weeks.

Mistake 6: Neglecting exercise: Even underweight horses need exercise. This promotes appetite, muscle development, and well-being. Of course, training must be adapted to the horse's condition; some underlying diseases mean that the horse should not be exercised at all or only very little.

Does your horse require comprehensive diagnostics? Altano clinics have state-of-the-art examination facilities. Contact us now.

Prognosis: Can my horse gain weight again?

The outlook depends heavily on the cause: if the underlying disease can be treated without leaving any residual problems, the prognosis for weight gain is favorable. This includes, for example, dental problems after treatment or optimization of husbandry and feeding management. Horses with chronic intestinal inflammation or stomach ulcers require permanent dietary management. Older horses can also regain weight with an adjusted diet, but they must receive permanent good feeding management. Diseases that cannot be treated have a poor prognosis for long-term weight gain. This applies to horses with tumors, chronic kidney failure, or horses in which the cause of weight loss cannot be found.  

In most cases, however, the prognosis is good if the cause is found and treated!

Conclusion: A systematic approach leads to success

If your horse is too thin, it is crucial to systematically investigate the cause. 

Assess the nutritional status objectively using the Body Condition Score. Start with the most common causes – dental check-up and feed review. If the cause is unclear, have a comprehensive diagnosis carried out. Optimize feeding gradually and patiently. Monitor progress regularly and adjust measures accordingly. In cases of chronic or unexplained weight loss: do not hesitate to carry out further diagnostics.

With the right approach and a little patience, most underweight horses can return to a healthy body weight and thus enjoy a better quality of life.

For better readability, we predominantly use the generic masculine in our texts. It goes without saying that all personal designations refer equally to all genders. The abbreviated form of language is used solely to improve comprehensibility and is to be understood in an unbiased manner.