Putting weight on a skinny horse can be a difficult and frustrating task. There are many different causes of weight loss in horses and feeding strategies will depend on why your horse is underweight in the first place.

Weight loss occurs when a horse is in a negative energy balance, meaning that they are consuming less caloric energy than they are using in a day.

Weight loss is especially common in senior horses which may be affected by multiple issues that contribute to reduced feed intake, poor digestion and nutrient use.

Poor dental health, gastrointestinal issues and low social standing can also contribute to weight loss.

When feeding to help a horse gain weight, many horse owners start with adding calories to the diet; however, it is important to first understand why your horse is losing weight and ensure they are healthy and in a comfortable environment.

It is also important to select the right energy sources to promote healthy weight gain without causing metabolic dysfunction.

Your veterinarian and equine nutritionist can help you get your horse to an ideal body condition.

Follow the steps in this article to develop a feeding plan to help your underweight horse gain weight. You can submit your horse’s information online and our nutritionists can help you design a diet to improve your horse’s body condition.

Is Your Horse Underweight?

How do you tell if your horse is underweight? Both body weight and body condition scores are important metrics to determine if your horse needs to gain weight.

Body condition scoring can also help you determine what your horse’s ideal body weight is for their size and breed.

Horses are considered underweight if they have a body condition of 4 out of 9 or less according to the Henneke Body Condition Scoring Scale. [1]

Body Condition Scoring is a way to estimate the amount of body fat (subcutaneous adipose tissue) that your horse has. The scale evaluates a horse’s condition by looking at six specific points on the body and assessing fat deposition.

Underweight horses will be classified as one of the following:

  • BCS of 4 – slightly underweight (moderately thin)
  • BCS of 3 – underweight (thin)
  • BCS of 2 – very underweight (very thin)
  • BCS of 1 – poor (emaciated)

With underweight, very underweight and emaciated horses, the neck, shoulders and withers are clearly accentuated, and the boney projections of the spine are visible to varying degrees.

Thin (Underweight) Body Condition Score Horse

We recommend conducting weight measurements and body condition scoring at least once per month as indicators of your horse’s nutritional and health status. Keep a log of these numbers to assess how your horse changes over time and to make adjustments in their diet as needed.

Body Condition Scoring for Horses

Causes of Weight Loss in Horses

There are many potential causes of weight loss in horses; it is usually a symptom of a much larger problem and not a disease in itself.

Weight loss or inability to gain weight effectively can be attributed to several factors including:

  • Dental issues
  • Social and behavioural issues
  • Musculoskeletal disorders
  • Temperature and environmental factors
  • Endoparasitism
  • Gastrointestinal disorders
  • Other underlying health issues
  • Malnutrition (nsufficient nutrient intake)
  • Starvation (due to neglect or abuse)

If your horse has shown recent weight loss or is struggling to gain weight, consult with your veterinarian to identify any medical issues that need to be addressed.

Once you have ruled out medical concerns, our equine nutritionists can help formulate an appropriate diet plan to help your underweight horse gain weight in a healthy manner.

How to Support Healthy Weight Gain

1) Identify and manage dental issues

Chewing is the first step in the digestive process that allows the horse to extract enough nutrients from its feed to support healthy body weight.

Horses rely on healthy teeth to grind and break down feed. Chewing increases the surface area of the food to initiate its digestion by enzymes. [3]

Dental issues are one of the most common reasons a horse may be losing weight. In a recent study by Tamzali and colleagues, 20% of underweight horses were diagnosed with dental problems. [2]

This primarily affects senior horses (over 15 years of age), of which up to 95% have dental abnormalities. [4]

Dental issues can range from sharp edges that cause mild discomfort when chewing to more serious cases of inflammation and pain.

Senior horses commonly develop gaps between their teeth, called diastemata, which can allow food to get stuck between the teeth and decompose, leading to inflammation and pain. This can make your horse reluctant to eat and result in weight loss.

More serious dental conditions such as equine odontoclastic tooth resorption and hypercementosis (EOTRH) can also arise with age and affect your horse’s ability to chew. [6]

Below are several steps you can take to support your horse’s dental health and help them chew comfortably and effectively.

  1. Monitor how your horse is eating: Look for quidding (dropping feed), food pocketing or overproduction of saliva
  2. Have their teeth floated: Your horse’s teeth should be checked at least once per year. They should be regularly floated (filed or rasped) to remove any sharp edges and keep the surface smooth
  3. Monitor senior horses more closely: Horses over the age of 15 should have their teeth checked every 6 months to keep an eye on common dental issues that arise with age
  4. Soak their hay: For horses that struggle to eat forage, soaking or steaming their hay might be beneficial to soften the fibres
  5. Replace their forage: For horses with advanced dental issues, alternatives like soaked hay cubes, beet pulp, hay extenders, soybean hulls and/or concentrate feeds may need to be fed in place of forages. In severe cases or for horses with no teeth left, these soaked mashed can make up 100% of the horse’s diet

Frequent monitoring of eating behaviour and dental health is important to identify issues with chewing.

2) Support gastrointestinal health

Proper function of the digestive system is critical for your horse’s overall health and for converting feed into usable forms of energy. When things go wrong in their digestive system, horses can lose weight quickly.

Gastrointestinal conditions such as stomach ulcers, inflammatory bowl disease, infiltrative bowel disease or hindgut ulcers may be causing your horse to lose weight.

For horses prone to digestive issues, a forage-first diet with minimal concentrate feeds will support gastric health and decrease the risk of hindgut acidosis.

Limit starch intake to be below 1 gram per kg of bodyweight per meal (500 grams of starch for a 500 kg horse), or no more than 2 grams of starch per kg bodyweight per day (1000 grams starch for a 500 kg horse). [19]

Monitor your horse’s fecal consistency as a sign of potential digestive issues. Conditions such as free fecal water syndrome (FFWS) can be a sign of impaired digestive health.

Changes in fecal consistent may also be a sign of dental health issues that affect your horse’s ability to break down fibres. [5]

3) Combat Intestinal Worms

Endoparasites, also known as intestinal worms, are another cause of weight loss in horses.

Parasites can be present with or without diarrhea and can negatively affect absorption of nutrients from the gut. Small strongyles (cyathostomins) are the most common type of parasitic infection in mature horses. [14]

Age does not appear to be a factor in parasitic risk but may influence the type of parasites your horse is likely to be affected by. Horses with Cushing’s / PPID appear to have higher parasite burdens. [15]

Resistance to dewormers (also referred to as anthelmintics) is a growing concern. Previous veterinary deworming protocols relied on a preventative, rotational deworming program that is ineffective against small strongyles. [14]

Fecal egg counts are strongly recommended to determine the parasite burden of your horse. [14] If the parasite burden is high, your veterinarian can identify the predominant species of parasite and prescribe an appropriate treatment.

Individualized, evidence-based deworming protocols are the way to go!

4) Address Musculoskeletal Disorders

Musculoskeletal disorders like arthritis can also cause weight loss in horses.

Arthritis can prevent your horse from properly accessing or chewing food. Arthritis affects up to 94% of horses over the age of 20 years. [11]

Grazing or lowering the head to eat can put added pressure on the forelimbs, neck and back. If arthritis is present, this can deter your horse from eating.

Musculoskeletal issues can also limit a horse’s natural foraging behaviours. If the pasture is icy or has uneven terrain, your horse may not feel comfortable moving around their paddock to eat.

Supporting their diet with joint supplements can provide some relief by improving joint comfort and mobility.

For horses that find it uncomfortable to lower their head to eat, feeding in raised hay nets and feeders can make eating more comfortable by putting less weight and pressure on sore joints.

Ensure these horses have easy access to both feed and water and, if turned out in a group, ensure they are not blocked from these resources by other horses.

Pain can also decrease your horse’s appetite; is important to address any musculoskeletal disorders with your veterinarian.

5) Address Other Health Issues

Other diseases such as liver disease and kidney problems can also cause weight loss in horses.

Liver disease is a fairly common cause of weight loss in horses and can be diagnosed by a veterinarian. It was found to account for up to 10% of weight loss cases admitted to a referral hospital. [2]

Consumption of poisonous plants like ragwort or mycotoxins from hay is a common cause of liver dysfunction.

Some medications can cause horses to lose weight or decrease their appetite. Pergolide (Prascend) is a medication to treat Cushing’s / PPID in horses. It can cause a decrease in appetite when horses first start treatment.

Discuss with your veterinarian if you feel your horse’s medication may be impacting their body condition before making any changes.

Other conditions that result in your horse becoming underweight include:

  • Cancer
  • Chronic Infections
  • Chronic Diarrhea
  • Neurological conditions (such as Equine Protozoal Myeloencephalitis)
  • Equine Infectious Anemia

If your horse is suspected of having these conditions, be sure to discuss concerns about weight loss with your veterinarian and equine nutritionists.

6) Enable positive social interactions

Bullying may be happening in your horse’s turnout group and could be contributing to weight loss.

Horses are highly social animals and establish clear social hierarchies when grouped. There are a number of benefits to allowing horses to interact with each other.

However, horses low in the pecking order can struggle to maintain a healthy body condition. [8]

Dominant horses in social groups have priority access to and guard resources like food and water. Horses lower in the social order may have reduced access to food and water. [9]

Research shows that horses higher in the social order tend to have higher body condition scores than horses lower in the social order. [8]

You can support your horse’s social behaviours while minimizing negative interactions by:

  • Ensuring there is enough space, food, and water for each horse: Provide food and water in multiple areas of the paddock to avoiding bullying at one source
  • Avoiding frequent changes in social groups: Introduction of a new horse, loss of a close friend or frequent regrouping can cause stress and aggression in horses, potentially reducing your horse’s appetite or limiting their access to food and water [10]
  • Separating horses that are lower in the pecking order: Separate these horses from the group to eat or use a feed bag (also called a nose bag). Older horses or those with dental issues might require more time to finish their food. Separating them from the group can be beneficial

In addition, behavioural issues such as stall walking, cribbing, pawing, hyperactivity, or weaving can increase your horse’s caloric requirements or decrease their appetite. These horses may struggle to maintain a healthy weight due to stress.

Supporting their natural behaviours and providing appropriate outlets for their boredom and frustration can help reduce negative impacts on appetite and feed intake.

7) Maintain a Comfortable Temperature

Your horse has a thermoneutral zone (TNZ), or a range of temperatures where their body expends little to no energy to maintain a comfortable body temperature. [12]

If temperatures fall below or ride above the TNZ, your horse has to expend energy to keep warm by shivering or keep cool by sweating and/or panting. These physiological responses increase your horse’s energy demands.

The process of eating and digesting food also creates a lot of heat through the thermic effect of food. If your horse is already too hot, they may avoid eating.

Dehydration can decrease your horse’s appetite. Dehydration commonly occurs in hot weather due to sweating, but it can also occur in cold weather when drinking water is too cold or frozen. [13]

It is important to ensure your horse is equipped to withstand weather extremes, particularly if they commonly experience changes in weight due to hot or cold weather.

In extreme cold weather, blanketing may be necessary. This is esoecially important for thin horses as it is more difficult for them to stay warm.

Horses need to be blanketed when temperatures drop below -15 to 5°C (5 to 41°F) depending on whether your horse is clipped or if they are acclimated to the weather. Rain, wind, or snow can also affect your horse’s lower critical temperature. [12]

To avoid inappetence linked to dehydration make sure your horse always has access to clean, fresh water. Water should not be too hot or too cold to encourage your horse to drink more.

Research shows that horses prefer heated water compared to near-freezing water. [13] Exercised horses prefer water around 20°C. [18]

If your horse is sweating heavily, it should be provided with electrolytes to replenish electrolytes lost in sweat. Horses should be fed 1-2 tablespoons of added salt per day and should be provided with plain free-choice loose salt at all times.

8) Provide Good-Quality Forage

Once health concerns and environmental issues have been ruled out for your underweight horse, dietary changes may be required to support weight gain.

A good-quality forage (hay or pasture) should be the main source of calories and nutrients for any horse. Forage should be provided ad libitum and horses should have constant access to forage to minimize time spend with an empty stomach.

Your horse should be eating at least 1-2% of their body weight in hay or pasture each day. For a 500 kg horse, that means they should consume 5 to 10 kg of forage (on a dry matter basis) per day.

Poor quality forage is a common cause of equine weight loss. It is recommended to have your horse’s hay analyzed so you know exactly how much caloric energy it provides.

Horses that need to gain weight may benefit from the inclusion of legume hay such as alfalfa or clover hay. These hays provide more calories than grass hay and also tend to be more palatable when harvested at an early stage of growth.

9) Ensure Vitamin and Mineral Requirements are Met

We’ve analyzed thousands of equine diets at Mad Barn including forage-only feeding plans and diets composed of concentrate feeds. In 90% of cases, one or more key vitamins or minerals falls below the recommended intake level to avoid deficiency.

Vitamin and mineral deficiencies can cause weight issues by affecting your horse’s appetite, digestive function and metabolic health.

In particular, low intake of zinc, copper, and iodine can cause your horse to have a low appetite.

Feeding your horse a ration balancer or vitamin and mineral supplement at the recommended rate will ensure that nutrient deficiencies are addressed and support a homeostatic energy balance.

10) Supplement with Additional Calories

If your horse’s underlying health has been addressed, they are consuming good quality forage, and they are still underweight, additional calories can be added as needed.

Energy sources composed primarily of fat and healthy digestible fibres should be used to increase the energy density of the diet. This can be in the form of beet pulp, soybean hulls, hay cubes, flaxseed or supplemental oils.

Mad Barn’s w-3 Oil can be added to your horse’s diet to support healthy weight gain at a feeding rate between 100 – 200 mL per day. W-3 Oil contains Flax oil and soybean oil enriched with the omega-3 fatty acid DHA to support a healthy inflammatory response.

w-3 Oil Essential Fatty Acid Supplement
  • Promotes joint comfort
  • Helps to fight inflammation
  • Skin & coat condition
  • Palatable source of Omega-3's

If these additives are insufficient, you can also add low-starch concentrate feeds to the diet. Avoid feeds that contain high amounts of sugars such as molasses or starches such as corn products. These calorie sources can negatively impact your horse’s digestive and metabolic health.

Your horse’s nutrition plan should be individualized to their specific needs and exercise load. Some horses are genetically or temperamentally predisposed to being “hard keepers.”

Hard keepers tend to require more calories in order to maintain healthy body weight. A 500 KG thoroughbred may require more feed per day than a 500 KG warmblood.

Once you have identified your horse’s individual needs, weight gain should be achieved gradually with supplemental calories being added to the diet slowly.

Example Diet to Support Weight Gain

It is always recommended to work with an equine nutritionist to formulate a feeding plan based on your horse’s individual health history and current body condition.

You can submit your horse’s information online and our nutritionists can assist you for free.

Below is a sample diet for a 500 KG (1100 LB) mature horse at maintenance to support gradual weight gain without relying on high-grain feeds.

Feed Weight Gain Diet
(Amount / Day)
Hay 10.5 kg
Beet pulp 0.5 kg (1 lb)
w-3 oil 100 ml (3 oz)
Omneity 120 grams (4 scoops)
Salt 30 grams (2 tbsps)
Diet Analysis
Digestible Energy (% Req) 123%
Crude Protein (% Req) 154%
NSC (% Diet) 8.9%

 

It is recommended to choose molasses-free beet pulp to avoid excess sugars in the diet. Soaking beet pulp in water for 10 – 15 minutes helps remove excess iron. This should be followed by a quick rinse.

Supplemental oils are a flexible energy source that allows you to increase the caloric energy of the diet without relying on grains or concentrate feeds.

Flax oil, canola oil, soybean oil, camelina oil and corn oil can also be used to add calories. In this sample diet, we have used Mad Barn’s w-3 Oil which is high in the omega-3 fatty acid DHA. This has an added benefit for supporting joint health, cardiovascular function, and respiratory health.

Conclusion

There are many potential causes of weight loss in underweight horses. Some horses are “hard keepers” and appear to require more calories to maintain a healthy body condition.

If your horse has a low body condition score, it is important to first identify the underlying reason that your horse is losing weight as opposed to just adding more calories to their diet.

Most of the time weight loss is fairly simple to diagnose and treat. Good communication with your veterinarian and nutritionist will help you design the right feeding program and support your horse’s overall health and well-being.

Is Your Horse's Diet Missing Anything?

Identify gaps in your horse's nutrition program to optimize their well-being.

References

  1. Henneke, D.R. et al. Relationship between condition score, physical measurements and body fat percentage in mares. Equine Vet J. 1983.
  2. Tamzali Y. Chronic weight loss syndrome in the horse: a 60 case retrospective study. Equine Vet Educ. 2006.
  3. Zwirglmaier, S. et al. Effect of dental correction on voluntary hay intake, apparent digestibility of feed and faecal particle size in horse. J Anim Physiol An N. 2011.
  4. Ireland, J. et al. Disease prevalence in geriatric horses in the United Kingdom: veterinary clinical assessment of 200 cases. Equine Vet J. 2012.
  5. Di Fillipo P.A. et al. Effect of Dental Correction on Fecal Fiber Length in Horses. J Equine Vet Sci. 2018.
  6. Rehrl, S. et al. Radiological prevalence of equine odontoclastic tooth resorption and hypercementosis. Equine Vet J. 2018.
  7. Hole, S.L. and Staszyk, C. Equine odontoclastic tooth resorption and hypercementosis. Equine Vet Educ. 2018.
  8. Giles, S. et al. Dominance rank is associated with body condition in outdoor-living domestic horses (Equus caballus). Appl Anim Behav Sci. 2015.
  9. Furiex, C. et al. Exploring aggression regulation in managed groups of horses Equus caballus. Appl Anim Behav Sci. 2012.
  10. Christensen, J.W. et al. Effects of repeated regrouping on horse behaviour and injuries. Appl Anim Behav Sci. 2011.
  11. Brosnahan, M.M. and Paradis, M.R. Demographic and clinical characteristics of geriatric horses: 467 cases (1989-1999). J Am Vet Med Assoc. 2003.
  12. Morgan, K. Thermoneutral zone and critical temperatures of horses. J Therm Biol. 1998.
  13. Kristula, M.A. and McDonnell, S.M. Drinking water temperature affects consumption of water during cold weather in ponies. Appl Anim Behav Sci. 1994.
  14. Kaplan, R.M. Drug resistance in nematodes of veterinary importance: A status report. Trends Parasitol. 2004.
  15. McFarlane, D. et al. Fecal egg counts after anthelmintic administration to aged horses and horses with pituitary pars intermedia dysfunction. J Am Vet Med Assoc. 2010.
  16. Jorgenson, G.M. et al. Effects of enrichment items on activity and social interactions in domestic horses (Equus caballus). Appl Anim Behav Sci. 2011.
  17. vanDeirendonk, H. et al. An analysis of dominance, its behavioural parameters and possible determinants in a herd of Icelandic horses in captivity. Neth J Zoo. 1995.
  18. Butudom, P. et al. Rehydration fluid temperature affects voluntary drinking in horses dehydrated by furosemide administration and endurance exercise. Vet J. 2004.
  19. Nadeau, J.A. et al. Evaluation of diet as a cause of gastric ulcers in horses. Am J Vet Res. 2000.