In North America, it is estimated that up to 51% of horses are overweight and up to 8% are obese [1][2][3]

Horses become overweight from a combination of factors, including insufficient activity and consuming excess calories.

A horse’s energy requirements depend on many factors such as age, breed, genetics, exercise, and life stage. [4] Some horses are easy keepers and are prone to gaining weight quickly

Excess weight causes systemic inflammation and puts the horse at risk of health concerns such as ­­­­metabolic dysregulation and laminitis. Being over-conditioned can also affect performance, joint health and soundness. [5]

If your horse is overweight, work with your veterinarian and an equine nutritionist to formulate a feeding and management plan to support healthy weight loss. This article will discuss key tips for feeding overweight horses to lose weight.

How to Tell if Your Horse is Overweight?

Body condition scoring (BCS) is a method of estimating your horse’s subcutaneous adipose tissue (body fat that accumulates directly under the skin).

The BCS scale rates your horse’s body condition from 1 to 9, with a score of 1 considered emaciated (very thin) and 9 considered very obese. [6]

A healthy horse should score a 5 on the 9-point scale. However, a score of 4 or 6 may also be acceptable, depending on the horse’s life stage, age and any health conditions it may have.

A score of 7 is considered overweight, and scores of 8 and 9 are considered obese. [4] [6]

Assessing Body Condition

As horses gain weight, fat accumulates over the horse’s whole body and in these six areas: [6]

  • Over the tailhead
  • Over the rump
  • Along the withers
  • Along the neck
  • Over the ribs
  • Behind the shoulder

By visually assessing and palpating these key areas, you can understand where your horse falls on the 9-point scoring system.

Follow the steps in this Guide to Body Condition Scoring your Horse to determine whether your horse is overweight and needs to lose body condition.

Studies show that horse owners often underestimate their horse’s body condition, particularly for overweight horses. [1] Ask your veterinarian or an equine nutritionist for a second opinion on your horse’s BCS score.

What Causes Overweight in Horses?

Any horse can become overweight or obese when their energy intake is not balanced with their energy expenditure. However, many animal- and environment-specific risk factors can increase a horse’s likelihood of becoming overweight or obese.

Risk factors for being overweight can include: [1][7][8][9]

  • Feed availability: Providing excess food, above requirements, can result in weight gain.
  • Feed type: Providing energy-dense forages and complete feeds can contribute to weight gain.
  • Breed: Cob types and ponies are at greater risk of becoming obese, compared to Thoroughbreds who are at a lower risk.
  • Exercise level: Horses at maintenance (pleasure riding or no riding) are more likely to be overweight than competition horses in regular exercise.
  • Management: Horses maintained exclusively on pasture are more likely to be overweight than horses kept in stalls with daily turnout.
  • Season: Access to free-choice pasture in the summer is associated with a greater risk of obesity.
  • Age: Horses over 4 years are at greater risk of becoming overweight, possibly due to lower activity levels.

Why Should I be Concerned if my Horse is Overweight?

It is important to maintain your horse at a healthy body condition.

Overweight and obese horses are at risk of several health complications including, but not limited to: [1][4][11][12][13][14][15]

Feeding the Overweight Horse

Feeding practices play a key role in both the treatment and prevention of obesity.

If your horse is overweight, it’s important to reduce the energy content of their diet to create a calorie deficit. Follow the tips below on forage selection and feed provision.

Increasing your horse’s activity level by introducing appropriate exercise can also promote weight loss and improve metabolic health.

For personalized help with managing an overweight horse, submit their information online to receive free diet evaluation. Our nutritionists can help you identify factors contributing to your horse’s weight gain and formuate a weight loss plan for your horse.

1) Eliminate Grains and Commercial Feeds

To lower your horse’s caloric intake, slowly decrease or eliminate grains and commercial feeds from their diet.

Grain-based complete feeds and sweet feeds provide a lot of additional calories that most horses don’t need. These feeds also contain high amounts of sugars and starch, collectively called non-structural carbohydrates (NSC).

Feeding excess NSCs also has negative implications for digestive health, behaviour, and metabolic function. Sugar and starch are rapidly digested and absorbed by the horse’s body, increasing blood sugar levels.

This triggers the release of insulin, a hormone that tells the body to store glucose (sugar) as glycogen in the cells. Diets that provide too much sugar and starch can cause excessive insulin production which leads to insulin resistance, high blood glucose, and metabolic syndrome. [16]

Removing excess calories by transitioning from commercial feeds and grains to a forage-based diet is an easy first step to helping your horse lose weight.

2) Reduce Other Energy Sources

Beet pulp and fat supplements are good energy sources for hard-keepers, horses in heavy work, or horses requiring extra calories to maintain weight.

However, these feeds should be reduced or removed from the diets of overweight horses.

Fat supplements and oils are particularly energy-dense, providing 9 kilocalories (kcal) per gram of feed.

3) Feed a Forage-Based Diet

Forage should make up the bulk of your overweight horse’s diet. Hay is high in fibre, which is fermented by microbes in the hindgut to produce volatile fatty acids (VFAs) – the ideal energy source for horses.

Feeding forage supports a healthy gut microbiome and enables the horse to express natural grazing behaviours, reducing the prevalence of stereotypies such as stall weaving and cribbing.

Forages also take longer for your horse to chew than concentrates, extending feeding time and reducing ulcer risk.

Hay is lower in energy than haylage or pasture, making it a better choice for overweight horses. [3] Feeding low-quality forages, such as late-harvest hay can also help to reduce energy intake.

Choose grass hays, such as Timothy or Bermuda hay, that are lower in protein, NSC, and digestible energy content. Energy-dense legume hays, such as alfalfa and clover, should be reduced or eliminated from the diet.

Obtain a hay analysis to understand how energy-dense your horse’s hay is and how much to feed.

4) Replace Hay with Straw

Chopped straw or chaff is a low-calorie forage that can replace up to 25% of your horse’s hay. Alternatively, free-choice straw can be provided with their hay ration as an additional fibre source.

When feeding straw, it is important to check for and remove any grain/seed heads. Slowly increase the quantity of straw in the diet by no more than 10% daily to give your horse’s gut time to adjust.

Additionally, your horse should have free-choice access to water and should be supplemented with salt to encourage drinking. This will reduce the risk of impaction colic when consuming straw.

5) Safely Limit Forage Intake

Overweight horses should be fed a minimum of 1.5% of their body weight in forage daily, unless otherwise recommended by your veterinarian. [3][17]

For a 500 kg (1100 lb) horse, this is equivalent to 7.5 kg (16.5 lb) of forage daily. Overweight horses should have their forage weighed out daily to ensure they are being fed the correct amount.

Feeding less than this amount can contribute to health conditions such as insulin resistance, hyperlipidemia, ulcers, and colic.

Forage-restricted horses also have higher rates of stereotypical behaviours, which are unwanted, repetitive behaviours with no clear function that develop in response to stress or boredom. Examples of stereotypies include:

Make any changes to the horse’s diet gradually. When restricting your horse’s forage intake, use a hay net or slow feeder to increase the time that your horse spends eating.

6) Soak your Horse’s Forage

Soaking hay or haylage in cold water can remove 24-43% of simple sugars. This reduces the caloric value of the forage, making it suitable for an overweight horse. [3]

Horse owners typically soak their hay for 30 – 60 minutes before feeding. Avoid soaking hay for more than 2 hours in warm conditions and feed immediately after soaking to prevent harmful bacterial growth. [3]

Soaking also removes some of the water-soluble mineral content of the forage. If soaking your horse’s hay, feed a vitamin and mineral supplement to replace any nutrient losses.

7) Restrict Pasture Access

Turnout on pasture is important for your horse’s well-being, but non-exercising horses can quickly exceed their energy requirements when grazing on mid-quality pasture. [22]

Access to pasture should be carefully controlled to limit calorie intake and prevent pasture-induced laminitis. [17]

Simply decreasing your horse’s time on pasture may not be sufficient for weight loss. Horses can consume up to 4 mcal per hour of turnout, meeting maintenance requirements in as little as 4 – 5.5 hours. [22]

Consider using a grazing muzzle to reduce your horse’s grass intake. Grazing muzzles decrease intake by 30 – 80%. [18][19]

Turn your horse out when levels of non-structural carbohydrates are lowest in grass, such as in the early morning. [17] Avoid turnout in frosty conditions and in overgrazed pastures when the fructan content of grass will be higher.

NSC levels will be highest in the spring when the grass is lush and growing quickly, in the fall just before winter, and in freshly cut grass. [17] Overweight horses may need to be removed from pasture at these times to avoid excess calorie intake.

8) Implement Pasture Management Strategies

In addition to controlling your horse’s access to pasture, the following grass management techniques can help to ensure your horse has an appropriate paddock to graze in.

  • Dry lots: Dry lots are fenced paddocks kept bare of grass. Turnout on a dry lot allows exercise while ensuring your overweight horse cannot consume excess calories. Provide access to low-calorie hay or straw in the dry lot.
  • Strip grazing: Strip grazing involves sectioning off parts of your pasture with fences so that horses can only graze mall strips at a time. Make sure your horse does not overgraze the field.
  • Track systems: Sometimes called paddock paradises, track systems involve creating a track around the outside of a field with fences. Food, water and shelter are provided at different locations around the track to promote movement.
  • Unimproved grasses: Turnout your horse on an unimproved, unfertilized pasture with native grass species Many improved grasses have been bred to increase energy content for grazing cattle, but these grasses can be problematic for overweight horses.

9) Meet Vitamin and Mineral Requirements

Hay alone will not meet all of your horse’s nutrient requirements. Horses on a restricted diet for weight loss are at greater risk of vitamin and mineral deficiencies.

Feed your horse a concentrated vitamin and mineral supplement that balances their diet without adding significant calories. Avoid ration balancers with a high feeding rate, as these can add unnecessary energy and protein to your horse’s ration.

Mad Barn’s Omneity premix is an ultra-low calorie vitamin and mineral supplement that is ideal for overweight horses. Omneity has been expertly formulated to balance the majority of forage-based diets and provides 100% organic trace minerals, complete B-vitamin fortification, and digestive enzymes for gut health.

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Your horse should also have free-choice access to loose salt to help meet their sodium requirements and to promote hydration.

10) Limit or Eliminate Treats

Studies show that horses fed extra treats are at a higher risk of obesity. [7]

Commercial treats are often high in NSC and supply extra calories that your overweight horse does not need. [3] Fruits and some vegetables can also contain excess sugar and should be avoided.

If you use treats as part of your horse’s training, opt for low-NSC forage-based options such as hay cubes or hay pellets. Make sure that these products do not contain added sugars like molasses.

How Fast will my Horse Lose Weight?

Horses fed 1.5% of their weight in forage are expected to lose approximately 0.5-1% body weight per week. Weight loss results will vary between horses depending on the caloric intake of forage and exercise level. [3]

If your horse is not losing weight, consult your veterinarian and nutritionist to identify any potential factors or health conditions inhibiting weight loss.

Your veterinarian may recommend further restricting their forage intake to 1% or 1.25% of their body weight . This must be done cautiously, and the horse must be closely monitored for adverse reactions or the development of stereotypies. [3]

Weight loss tends to slow or plateau after 12 weeks of calorie restriction at which point it may be necessary to further limit your horse’s energy intake or to increase their exercise routine. [3]

Medications

If the feeding and management recommendations listed above do not promote adequate weight loss in your overweight horse, your veterinarian may consider medical treatment.

Thyroid hormones play a role in regulating your horse’s metabolic rate. Some horses with low thyroid hormone levels may have trouble losing weight and benefit from medication.

Levothyroxine sodium is a synthetic form of thyroid hormone. In one study, horses receiving levothyroxine for 48 weeks experienced significant weight reductions and improved insulin sensitivity. [21]

Metformin is another pharmaceutical drug used to increase insulin sensitivity in horses. It has been proposed as a weight loss therapy for horses with metabolic dysfunction, but initial studies suggest it has low oral bioavailability in horses. [22]

Maintaining your Horse’s Weight

Once your horse has reached an appropriate body condition, work with your nutritionist to formulate a long-term weight management plan that considers both diet and exercise routine.

Your horse’s digestible energy intake should be balanced with their energy requirements to maintain a healthy body weight. Continue to feed a forage-based diet with adequate vitamins and minerals. [22]

Assess your horse’s body condition at least once per month to ensure they remain at a healthy weight. Use an equine weight tape to quickly monitor for changes and adjust feeding and management accordingly. [4][6]

Submit your horse’s information online for a free diet evaluation from Mad Barn’s qualified equine nutritionists. Our nutritionists will help you formulate a weight loss feeding plan that is customized to your horse’s physiological status, feeding situation, breed, workload and individual requirements.

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References

  1. Kosolofski, H.R. et al. Prevalence of obesity in the equine population of Saskatoon and surrounding area. Can Vet J. 2017.
  2. Christie, J.L. et al. Demographics, management, and welfare of nonracing horses in Prince Edward Island. Can Vet J. 2004.
  3. Durham, A.E. et al. ECEIM consensus statement on equine metabolic syndrome. J Vet Intern Med. 2019.
  4. Geor, R.J. et al. Dietary management of obesity and insulin resistance: countering risk for laminitis. Vet Clin North Am Equine Pract. 2009.
  5. Harker, I.J. et al. The body condition score of leisure horses competing at an unaffiliated championship in the UK. J Equine Vet Sci. 2011.
  6. Henneke, D.R. et al. Relationship between condition score, physical measurements and body fat percentage in mares. Equine Vet J. 1983.
  7. Giles, S.L. et al. Obesity prevalence and associated risk factors in outdoor living domestic horses and ponies. PeerJ. 2014.
  8. Robin, C.A. et al. Prevalence of and risk factors for equine obesity in Great Britain based on owner-reported body condition scores. Equine Vet J. 2015.
  9. Frank, N. et al. Physical characteristics, blood hormone concentrations, and plasma lipid concentrations in obese horses with insulin resistance. J Am Vet Med Assoc. 2006.
  10. Hitchens, P.L. et al. Prevalence and risk factors for overweight horses at premises in Sweden assessed using official animal welfare control data. Acta Vet Scand. 2016.
  11. Geor, R.J. Metabolic predispositions to laminitis in horses and ponies: obesity, insulin resistance and metabolic syndromes. J Equine Vet Sci. 2008.
  12. Walshe, N. et al. A multiomic approach to investigate the effects of a weight loss program on the intestinal health of overweight horses. Front Vet Sci. 2021.
  13. Johnson, P.J. et al. Medical implications of obesity in horses—lessons for human obesity. J Diabetes Sci Technol. 2009.
  14. Vick, M.M. et al. Obesity is associated with altered metabolic and reproductive activity in the mare: effects of metformin on insulin sensitivity and reproductive cyclicity. Reprod Fertil Dev. 2006.
  15. Speakman, J.R. Obesity and thermoregulation. Handb Clin Neurol. 2018.
  16. Shepherd, M.L. et al. Effects of high and moderate non-structural carbohydrate hay on insulin, glucose, triglyceride, and leptin concentrations in overweight Arabian geldings. J Anim Physiol Anim Nutr (Berl). 2012.
  17. Frank, N. et al. Equine metabolic syndrome. J Vet Intern Med. 2010.
  18. Frank, N. et al. Effects of long-term oral administration of levothyroxine sodium on glucose dynamics in healthy adult horses. Am J Vet Res. 2008.
  19. Sommardahl, C.S. et al. Effects of oral administration of levothyroxine sodium on serum concentrations of thyroid gland hormones and responses to injections of thyrotropin-releasing hormone in healthy adult mares. Am J Vet Res. 2005.
  20. Glunk, E.C. et al. The effect of a limit-fed diet and slow-feed hay nets on morphometric measurements and postprandial metabolite and hormone patterns in adult horses. J Anim Sci. 2015.
  21. Frank, N. et al. Effects of long-term oral administration of levothyroxine sodium on glucose dynamics in healthy adult horses. Am J Vet Res. 2008.
  22. Becvarova, I. Scott Pleasant, R. Managing Obesity in Pasture-Based Horses. Vetlearn.com. Compendium: Continuing Education for Veterinarians®. 2012.
  23. Hustace, J. et al. Pharmacokinetics and bioavailability of metformin in horses. American Journal of Veterinary Research. 2009.