Equine Obesity Management: How to Spot It and Prevent It

Equine obesity is one of the most common welfare problems in British horses and ponies, and one of the hardest to see in your own field. When owners across Great Britain were asked to condition score their own animals, they rated 31.2% of 792 horses and ponies as fat or very fat (Robin and colleagues, Animal Health Trust, Equine Veterinary Journal, 2015, PMID 24735219). Excess fat is not a cosmetic problem. It travels with insulin dysregulation, it is linked to laminitis, and it loads every joint the horse owns. It is also largely within an owner's control. This guide covers how to recognise an overweight horse honestly, why good-doers gain weight so easily, and how to run a safe, vet-supported weight-loss plan that keeps your horse sound and healthy for years to come.

What Is Equine Obesity?

Obesity is a build-up of body fat to the point where it harms health. Because horses come in every size from a Shetland to a Shire, fat is judged with a condition score rather than a number on the scales. On British yards the usual tool is the British Horse Society's 0 to 5 fat score, on which the BHS describes 4 as fat and 5 as obese. Much of the research literature uses the American 1 to 9 scale instead, where studies such as Giles and colleagues (2014) class 7 or above as obese. The two scales are explained side by side in our guide to horse body condition scoring.

How common is obesity in horses? The answer depends on who is scoring and which animals are counted, which is why published figures vary so much:

Owner scoring is a known weak point in figures like these. A University of Liverpool study that interviewed UK leisure horse owners, professionals and online forum users (Furtado and colleagues, Equine Veterinary Journal, 2021, PMID 33002214) found owners struggled to separate obesity from the shape they believed the horse was "meant to be", especially in native ponies and cobs. Some described a horse as an ideal weight in the same breath as calling it "like a Thelwell". The 2019 European College of Equine Internal Medicine (ECEIM) consensus statement on equine metabolic syndrome notes that several studies have found owners of obese horses tend to underestimate their condition, and that when so many horses are fat, fat starts to look normal.

How to Tell If Your Horse Is Overweight

Your eyes are the least reliable tool you have, because they get used to the horse you see every day. A fat horse has to be felt as well as looked at, and its progress has to be written down.

Fat Scoring on the BHS 0 to 5 Scale

The British Horse Society's fat scoring guide divides the horse into three areas, the neck, the middle and the hindquarters, and scores each one from 0 to 5. A healthy fat covering is 2.5 to 3 out of 5 unless your vet advises otherwise. Fat feels spongy and muscle feels firmer, with one important exception: the BHS singles out dangerous crest fat, which can feel hard and be difficult to move from side to side. The BHS describes the top two scores like this:

• Score 4, fat: the shape of the muscles can no longer be seen, spongy fat can be felt along the crest, behind the shoulder and across the hindquarters, the ribs can only be felt with firm pressure, a gutter is forming along the spine and an "M" shape is starting to show over the quarters.
• Score 5, obese: a wide neck with a large, firm crest, ribs that can be neither seen nor felt, a flat back, pockets of fat across the body, a point of hip and pelvis that can no longer be felt, and a deep gutter along the spine with a definite "M" shape from behind.

The middle takes practice. The BHS method is to place your hand about a hand's width behind the withers and follow the shape across the horse's back. On a horse of healthy weight your hand follows the arch over the spine and you can feel the backbone. When fat builds up on either side until it sits higher than the spine, your hand lies flat and a gutter forms along the top line.

Two conditions make scoring harder. The BHS points out that horses with equine metabolic syndrome tend to carry abnormal fat pads on the neck and hindquarters, while horses with Cushing's disease may combine abnormal fat with muscle wastage, a pot belly and visible ribs. A horse can therefore show its ribs and still have a metabolic problem, which is one reason to involve your vet rather than rely on the score alone.

If you read American advice you will meet the Henneke body condition scoring system, a 1 to 9 scale published by Henneke, Potter, Kreider and Yeates in the Equine Veterinary Journal in 1983 (PMID 6641685). Many of the research papers quoted in this article use it. Just be sure which scale a number belongs to before you act on it, because the same digit means very different things on each.

The Cresty Neck

A thick, hard crest deserves its own attention. Researchers score it separately with the Cresty Neck Score, which runs from 0 to 5. In a University of Bristol study of 96 UK leisure horses (Giles and colleagues, BMC Veterinary Research, 2015, PMC4347557), 45.83% had a score of 3 or more at the end of winter and 33.33% at the end of summer. Prevalence was higher in ponies under 14.2hh than in horses, and native UK breeds were most at risk. That winter peak is the opposite of the pattern for overall fatness, and the authors could not say whether crest fat really increases in winter or is simply harder to judge under a winter coat. Either way, a pony that has slimmed down over winter may still be carrying a crest.

The crest matters because it is linked to laminitis. In a closed herd of mainly Welsh and Dartmoor ponies studied at Virginia Tech (Carter and colleagues, Equine Veterinary Journal, 2009, PMID 19418747), a body condition score of 7 or more out of 9, a Cresty Neck Score of 4 or more out of 5, and raised blood insulin and leptin all predicted which ponies went on to develop laminitis at grass.

Weigh Tapes, Weighbridges and Belly Girth

The BHS recommends using a weigh tape alongside fat scoring every two weeks. Weigh tapes are not perfectly accurate, but they show whether a horse is maintaining, losing or gaining weight. A weighbridge gives a true figure: the BHS brings one to yards, and your vet practice or feed merchant may offer the same service.

Condition scores are slow to move, so do not judge a diet by the score alone. When Dugdale and colleagues at the University of Liverpool restricted five overweight pony mares to a measured diet for 12 weeks (Equine Veterinary Journal, 2010, PMID 20840575), the ponies lost weight steadily but their condition scores stayed the same, while heart girth and belly girth fell. A second Liverpool study by Argo and colleagues (The Veterinary Journal, 2012, PMID 23117030) also found condition scoring a poor estimate of body fat, while changes in belly girth tracked the loss. A tape measure around the widest part of the belly, taken at the same spot each time, is one of the most useful things you can own. Photographs from the same angle every fortnight make the change visible to the rest of the household too.

What Causes Equine Obesity?

At its simplest, a horse gets fat when it takes in more energy than it uses, over weeks and months. The BHS explains why so many modern horses end up on the wrong side of that balance: draught types, cobs and native breeds evolved to survive cold, wet winters on poor grazing, and many now have good grass all year round, milder winters, rugs and stables. They no longer need to burn energy to keep warm, and the calories keep coming.

Breed and the Good-Doer

In the Bristol study, breed was the risk factor most strongly associated with obesity, and it dominates the Robin data too. In the Robin study of 792 British horses and ponies, compared with Thoroughbreds:

• draught types had 7.3 times the odds of being obese
• cob types had 5.6 times the odds
• Welsh breeds had 3.5 times the odds
• other native breeds had 3.2 times the odds
• animals their owners described as "good doers" had 3.7 times the odds of animals that readily held a normal weight

None of this is a criticism of the breeds. A Welsh Cob, a traditional cob or a Shetland pony is built to make the most of very little. The semi-feral Carneddau ponies of Eryri still live out on their mountain all year without supplementary feeding. Put the same kind of pony on a lowland paddock of improved grass and it will turn that grass into fat with remarkable efficiency.

Grass, and More Grass

Grass is an easy calorie source to overlook, because it arrives without a scoop. The ECEIM consensus notes that horses eat more dry matter when pasture is freely available, that high-sugar pasture has been shown to worsen high insulin in ponies, and that simply shortening turnout has a limited effect because horses and ponies eat quickly when time is short. Grass does not stop in winter either: Aimi Duff of Rainbow Equine Hospital told Horse & Hound that grass grows whenever the temperature is above 4C, so a mild winter day can deliver a surprising amount of sugar.

Workload and Use

The Robin study found animals used for pleasure riding had 2.5 times the odds of obesity, and non-ridden animals 2.9 times, compared with competition horses. Gentle work is not always enough to make a difference. In the Bristol study, low-intensity structured exercise showed no association with obesity and supplementary feed was not a strong predictor, and the authors concluded that for horses living out for six hours or more a day, both had limited or no effect on obesity levels.

The Winter That Never Comes

Horses evolved to lose condition over winter and put it back on in spring and summer. As Horse & Hound's winter weight-loss feature puts it, most modern horses never lose that weight, because they are well fed and rugged up through the cold months, then gain again the following summer. Aimi Duff notes in the same piece that fermentation in the hindgut produces considerable heat, that a winter coat is the horse's own rug, and that a fat unclipped horse may already be wearing the equivalent of a heavyweight. The Bristol data fit this: obesity rose from 27% at the end of winter to 35% in summer, and the obese horses showed less seasonal change than the rest.

The Health Risks of Equine Obesity

Fat is metabolically active tissue, not just stored weight, and carrying too much of it changes how the whole body works.

Equine Metabolic Syndrome and Insulin Dysregulation

The condition most closely tied to obesity is equine metabolic syndrome (EMS), in which the horse cannot regulate its insulin normally. The ECEIM consensus statement (Durham and colleagues, Journal of Veterinary Internal Medicine, 2019, PMID 30724412) is careful on cause and effect: obesity is no longer seen as the sole cause of EMS but as a commonly associated feature that makes insulin dysregulation worse when it is present. Fat tissue produces hormones of its own, including leptin and adiponectin, which affect how the body handles sugar. The practical point is that a fat horse should be tested: the consensus says the need for dietary control should be judged on the degree of insulin dysregulation as well as on bodyweight, so the blood result helps your vet decide how strict the plan needs to be.

The Royal Veterinary College cohort shows why. Of the 446 ponies Menzies-Gow and colleagues followed, 44 (9.9%) were reported to have had laminitis within three years. The factors significantly associated with who developed it were blood markers: low adiponectin and high insulin.

Laminitis

Laminitis is the complication owners fear most, and weight gain sits squarely among its risk factors. In a case-control study of 1,010 veterinary-registered horses and ponies in Great Britain, 191 of them laminitis cases (Wylie and colleagues, Animal Health Trust, The Veterinary Journal, 2013, PMID 24070987), the factors associated with increased risk included weight gain in the previous three months, new access to grass in the previous four weeks, and existing EMS or Cushing's disease. Summer and winter carried more risk than spring.

There is no safe season. A cohort study of 1,070 horses and ponies in Great Britain (Pollard and colleagues, Equine Veterinary Journal, 2019, PMID 30516850) found laminitis occurred throughout the year with no significant difference between seasons. So watch the horse rather than the calendar: in the Wylie study the risk factors were recent weight gain and new access to grass, whatever the month. Our guide to treating and managing a laminitic horse covers the disease itself.

Joints, Heat and Other Effects

Writing in Horse & Hound, Kieran O'Brien MRCVS lists obesity as a contributor to soft tissue injuries, osteoarthritis and colic, and notes it has been associated with equine asthma. Every extra kilogram is carried by the same four legs, which matters most for an older horse already managing arthritis. Fat is also, in Aimi Duff's words, "a great insulator", which works against a horse in hot weather.

Cushing's Disease Is a Separate Problem

Pituitary pars intermedia dysfunction, better known as Cushing's disease or PPID, is a separate disease of the pituitary gland. It matters here because it can bring insulin dysregulation of its own and, as the BHS notes, an unusual fat distribution that confuses scoring. The ECEIM consensus recommends that where PPID is diagnosed, it is treated with pergolide to limit its effect on insulin regulation. Our article on Cushing's disease in horses covers the condition in more detail.

Equine Obesity Management: A Safe Weight-Loss Plan

Every successful plan does two things: it reduces the calories going in and increases the calories going out. The most detailed published guidance on how to do that safely is the ECEIM consensus statement, which sets specific targets for obese and insulin-dysregulated horses. The figures below are taken from it unless another source is named. They are starting points to agree with your vet, not a substitute for one.

Start With Your Vet

Ask your vet to examine the horse and check for EMS and PPID before you start. The ECEIM consensus says success should be judged by retesting insulin regulation, not just by weight lost, and recommends monthly veterinary re-examinations once a diet begins, becoming less frequent (every 3 to 12 months) once good progress is made. A horse with current or recent laminitis needs a veterinary plan before any change to exercise.

Harry Carslake of the University of Liverpool, speaking to Horse & Hound, suggests recording the following before you and your vet or nutritionist build a plan:

• everything the horse eats over 24 hours, measured in kilograms rather than scoops or armfuls
• how many hours a day it spends at pasture
• how much exercise it does each week
• any medical conditions that need to be taken into account

How Much Forage to Feed

Forage stays the foundation of the diet: cutting it too hard is unsafe for the gut and for the horse's wellbeing. The ECEIM consensus recommends a forage-based ration totalling 1.4% to 1.7% of the horse's current bodyweight per day as fed, which is 1.25% to 1.5% as dry matter. For a 500 kg horse that works out at 7 to 8.5 kg of hay a day. Only in exceptional cases that prove resistant to weight loss does the consensus go as low as 1.15% as fed, and then only with monitoring. It also advises phasing the restriction in over a week or two rather than starting abruptly.

Some horses simply lose weight more slowly than others. In the Argo study, 12 overweight horses and ponies fed at 1.25% of bodyweight as dry matter lost between 0.16% and 0.55% of their week-one weight each week, and about 65% of that variation came down to the individual animal rather than the diet. If your horse is one of the slow ones, that is not proof you are doing it wrong, but it is a reason to go back to your vet rather than quietly cutting more.

Ways to make a restricted ration last:

• Weigh the daily ration on a spring balance and split it into several smaller meals.
• Use a small-holed hay net, or double or triple fine-mesh nets as Aimi Duff suggests, to slow eating. The ECEIM consensus notes hay nets extend eating time on a restricted ration.
• Avoid long periods with nothing to eat. If you are worried about gastric ulcers during restriction, Aimi Duff's advice is to consult your vet.
• The ECEIM consensus supports replacing up to 30% of the forage with straw, introduced gradually, and advises watching droppings for early signs of impaction colic. Kieran O'Brien adds that the horse needs healthy teeth for this. Our guide to hay alternatives covers straw and other low-calorie fibres.
• A horse on a restricted ration may start eating its bed. The ECEIM consensus suggests rubber matting may be worth considering in some cases.

Choosing and Testing Hay

The ECEIM consensus recommends forage with a non-structural carbohydrate (sugar plus starch) content below 10% for horses with insulin dysregulation, and it advises against haylage for these horses: insulin responses to haylage are greater than to hay of the same sugar content, and horses tend to find it more palatable. Kieran O'Brien makes a useful point about choosing hay by eye: the calorie content depends on the age of the grass when it was cut and the grass species, not on how old the bale is. The only way to know what is in your hay is to have it analysed, and our article on nutrients in hay explains how to read the report.

Soaking is a tool, not a guarantee. The ECEIM consensus recommends soaking for horses with insulin dysregulation, but how much sugar it removes varies widely. Longland and colleagues (Veterinary Record, 2011, PMID 21652661) found soaking a range of UK hays removed an average of 27% of water-soluble carbohydrate, with a range of 6% to 54%, and seven of the hays they tested were still above the level suggested for laminitis-prone animals afterwards. Have the hay analysed, and if it is still too high, find different hay. The ECEIM consensus also warns that long soaks in warm conditions encourage bacterial growth, so keep soaks short in warm weather.

Cut Out the Extras

The ECEIM consensus says grains and cereal-based feeds, fruit and vegetables such as carrots and apples, and treats should generally be removed from an obese horse's diet, and that high-fat feeds should also be avoided because of their energy content. Because forage alone, and especially soaked forage, can leave gaps, it recommends a ration balancer to cover protein, vitamins and minerals. Supplements sold to help horses lose weight are popular, but the consensus describes their effectiveness as questionable or unproven.

Managing Grazing

Grass is where many diets come unstuck. For horses with insulin dysregulation, the ECEIM consensus advises preventing pasture access during the first 6 to 12 weeks of dietary restriction, because even partial grazing is so hard to measure. Once insulin regulation is under control, some grazing can come back. The options for doing that include:

• A grazing muzzle. The ECEIM consensus notes that muzzles reduce intake and can also increase foraging time and exercise, and Kieran O'Brien adds that they let bonded ponies live together. He advises not leaving a muzzle on for more than 10 to 12 hours at a time, checking regularly for rubbing and tooth wear, and never turning the horse back out unmuzzled afterwards, because a hungry pony will binge.
• Strip grazing. O'Brien suggests an electric fence moved forward a little each day, with a back fence to stop the horse eating the regrowth behind it.
• A track system. Fencing off the perimeter of the field into a track, as Aimi Duff describes, encourages more movement than a conventional paddock.
• A bare paddock with weighed forage. This keeps the horse out, moving and with company while you control exactly what it eats.

Exercise

Exercise burns calories and can improve the way the body handles insulin, although the ECEIM consensus is frank that results in horses are mixed and lower levels of exercise have often disappointed. It sets out minimum recommendations, which it describes as opinions extrapolated from medical research and clinical experience:

• Horses with insulin dysregulation and no laminitis: low-to-moderate intensity exercise, meaning canter to fast canter ridden or unridden, for more than 30 minutes, more than five times a week.
• Horses that have had laminitis and whose feet have recovered and are stable: low-intensity exercise on a soft surface, fast trot to canter unridden, for more than 30 minutes, more than three times a week, watching carefully for any lameness.
• Horses with current or recent laminitis: these recommendations do not apply. Your vet decides when exercise can start.

Build up gradually from the horse's current fitness. Consistency matters more than the odd big session: in a small University of Kentucky study (Powell and colleagues, Equine Veterinary Journal supplement, 2002, PMID 12405664), seven days of 30-minute trot sessions improved insulin sensitivity in three obese mares, but the improvement had gone within nine days of stopping. Aimi Duff's list of ways to keep a horse moving in winter includes brisk walking, lungeing, the horse-walker and work over poles. Long-reining is another way to put a pony that is too small to ride into proper work. Our equine fitness plan has ideas for structuring the weeks.

How Fast Should a Horse Lose Weight?

Slowly. The ECEIM consensus targets a loss of 0.5% to 1% of bodyweight per week, carefully monitored so the target is reached but not exceeded. For a 500 kg horse that is 2.5 to 5 kg a week. Faster losses have been linked to rising blood fats, which is the road to hyperlipaemia. The consensus flags pregnant mares, miniature horses, Shetland ponies and donkeys as the animals in which blood fats most need watching during a diet. A dieting pony, miniature or donkey that goes off its feed or seems dull needs your vet, not another day of the diet.

Expect the numbers to behave oddly at first. In the Dugdale study the ponies lost 4.3% of their weight in the first week and about 0.7% a week after that; the ECEIM consensus attributes the bigger first-week drop to reduced gut fill. The ECEIM consensus also warns that after about 12 weeks the same level of restriction may stop working as the horse's metabolic rate adapts, at which point your vet may suggest tightening the diet or adding exercise.

Monitoring Progress

• Fat score and weigh tape every two weeks, as the BHS recommends, and use a weighbridge when you can.
• Measure belly girth at the same spot each time. Kieran O'Brien notes that at a 12-week check the fat score and weigh tape can look virtually unchanged even when the horse has genuinely lost weight, and belly girth is the better gauge.
• Harry Carslake suggests reviewing the feeding plan with your vet or nutritionist after four to six weeks.
• Keep a written record. A diary of scores, measurements, forage weights and turnout hours is what lets you and your vet see whether the plan is working.

Preventing Equine Obesity Year-Round

Keeping weight off is far easier than taking it off. The habits that prevent equine obesity are the same ones that treat it, applied before the problem starts:

• Score all year, not just in spring. Two-weekly fat scoring and a weigh tape, as the BHS recommends, catch weight gain while it is still small.
• Let winter do its job. Rug for the horse in front of you, not for how cold you feel. Our horse rugging guide covers choosing the right weight, and Aimi Duff suggests clipping a fat horse whose weight is not shifting once rugs come off.
• Plan for flushes of grass. New access to grass in the previous four weeks was a laminitis risk factor in the Wylie study, so have muzzles, strip fencing or a bare paddock ready before the grass comes rather than after.
• Match hard feed to real work. Harry Carslake's view is that unless a horse is in a high level of work, most need minimal or no concentrate beyond a balancer.
• Count the treats. Apples, carrots and handfuls of mix add up. Low-sugar fibre treats exist if you want something to reward with.
• Know your horse's type. If you own a native, a cob or a draught cross, plan for it to gain weight easily and manage it from day one.

Yard culture matters too. Kieran O'Brien notes that some livery yard owners will not allow the grazing and management changes an overweight horse needs, and the ECEIM consensus recognises that peer pressure from other owners on the same yard can be a real barrier. If your yard will not support a weight-loss plan, that is worth a conversation, and your vet's written advice can help. A horse kept at a healthy weight is sounder, more comfortable and far less likely to end up on box rest with sore feet.

Frequently Asked Questions