Should I be worried that my horse is overweight?

Should I be worried that my horse is overweight?



Equine obesity is not something that can be taken lightly. Excess body fat has the possibility to severely affect your horse’s physical health and performance. Unhealthy fat deposits are a serious health concern are is linked to myriad health issues such as laminitis, insulin resistance, joint and skeletal issues, osteoarthritis, reproductive issues, inflammation and so on.


Science has shown that excess fat is more than just unsightly lumps or a cresty neck. Unfortunately the fat doesn’t just sit there and mind its own business! Fatty tissue is an active tissue that secretes hormones and inflammatory proteins that can negatively affect your horse’s health.


Sadly, equine obesity is on the rise. Studies in the U.K. reveal that around 45% of pleasure horses and ponies are fat to obese. The figure in the U.S.A. is around 50% and in Australia about 25% of horses are unhealthily overweight. Unfortunately, owners frequently underestimate the condition of their horse, especially when they’re overweight.



What’s the cause of equine over-conditioning?


The increase of obesity in horses isn’t caused by just one thing, it’s a combination of several factors related to husbandry and feed. Unfortunately there is a significant lack of education about equine nutrition. Surveys repeatedly show that horse owners get most of their nutrition advice from feed store employees and feed companies, rather than from independent nutritionists, academics in the nutrition field, or veterinarians. There is almost always a huge gap between what a feed store employee tells you your horse needs and what your horse actually needs. Most of the time feed store employees do not have any real understanding of the basic principles of equine nutrition and are trying to sell you as many (expensive) things as possible. The key to feeding your horse is keeping it simple, and keeping it simple does not usually mean a huge profit for the store!


Overfeeding of grain-based concentrates/pellets (grain is the the major ingredient in 95%+ of pelleted feeds) is almost certainly a contributing factor to equine over-conditioning/obesity. While most feed store employees will try and tell you your horses needs concentrates on a daily basis, whether in or out of work and regardless of condition, most nutritionists will argue that concentrates simply aren’t required for a large majority of pleasure horses.

Combined with over-feeding is the issue of owner perceptions of condition. Not only do many owners not realise their horse is overweight, but many don’t consider it to be an problem or health concern until it develops into laminitis. What’s worse is that some owners seek an over-conditioned physique as it is what’s favoured in halter or show classes. Fat and muscle can be aesthetically similar so a fat horse can look like a horse with great topline and muscle definition to an untrained eye.

Owners also often overestimate the amount of exercise their horses gets and underestimate the amount it needs in order to lose weight. Of course any exercise is good exercise, but for an overweight horse to lose a significant amount of weight around 40 minutes of brisk trotting under saddle or on the lunge five times per week is about the minimum required for serious changes to occur.

It’s not all our fault as owners though, the largest contributing factor to obesity in horses is today’s hay and pasture quality. So many of today’s pastures are improved, irrigated and mostly composed of plants intended for cattle and are just too rich for horses. Hay is usually grown for cattle and is cut at the stage of growth and time of day to ensure it contains maximum sugar and starch as this is what is desirable for cows! There are farmers who grow hay specifically for horses so be sure to look for it if this is what your horse needs. This ‘horse specific hay’ should come with a pasture analysis so you can make sure it's low in sugar and starch.

Another important factor affecting weight and conditioning is your horse’s breed. Some horses (and horse breeds) are genetically predisposed to suffer from metabolic issues and obesity. Horses that are naturally cresty (even if not overweight) or are easy-keepers have slower metabolisms and are more likely to gain and maintain weight easily. Breeds that are more genetically disposed to have metabolic issues include Andalusians, Quarter Horses, Morgans, warmbloods, drafts and pony breeds (breeds that have historically adapted to living on sparse food sources).

Over-conditioning and Insulin Resistance (IR)

Insulin resistance (IR) is a hormonal disorder that most commonly occurs in horses with equine metabolic syndrome (EMS) and in horses with Cushing’s disease (pituitary pars intermedia dysfunction, PPID), although not all horses with PPID have IR.

Insulin is the hormone which facilitates the movement of glucose (which increases post-meal) from the bloodstream into various cells, thereby lowering blood glucose concentrations back to baseline. A horse that doesn’t respond to the effects of insulin (insulin helps control blood sugar levels) is referred to as insulin resistant. Horses with IR cannot control blood glucose concentrations. Therefore, after a meal the amount of glucose in the blood can be very high and stay that way for several hours causing the pancreas to secrete even more insulin in an effort to reduce the amount of blood glucose. The resulting high amount of insulin in the blood is a sign of IR.

The consequences of insulin resistance are something we should all be concerned about. High glucose concentrations are believed to be toxic, and can directly damage the pancreas and blood vessels. Extreme excess insulin has been shown to directly cause laminitis in ponies and it is possible that high blood glucose concentrations could trigger laminitis even if the horse isn’t IR.

Several studies have found links between obesity and insulin resistance and a correlation between body condition score and resting insulin levels. It’s been shown that horses with higher body condition scores (> 7 on the Henneke scale) are less sensitive to insulin. At this point in time a direct relationship between fatty tissue and insulin function is not completely understood and it is unknown if obesity causes insulin resistance or if insulin resistance contributes to the development of obesity.

Nonetheless, the increased risk of laminitis associated with either obesity and/or insulin resistance makes this a very important issue to understand. Studies in humans have suggested that fat can be more or less dangerous depending on where it’s stored. This has led to suggestions that regional fatty deposits in the horse, i.e. a cresty neck, the dimpling of fat in the abdomen or hindquarters and fatty deposits near the dock may increase insulin resistance and laminitis in horses.

How do I know if my horse is Insulin Resistant?

Knowing if your horse is insulin resistant is an excellent first step towards managing its health and condition. Regardless whether your horse is IR or just fat (or both!) it should be managed in a similar way. Note that a horse can be insulin resistant and a normal weight, or be obese and sensitive to insulin. If you have an obese horse that is constantly footsore or lame it is more likely to be insulin resistant, although horses that appear to be perfectly healthy have been shown to have lower insulin sensitivity and are more likely to develop problems later on.

I recommend getting in touch with your vet to discuss how to diagnose whether your horse is IR or has EMS or PPID.

What can I do if my horse is overweight or Insulin Resistant?

The first thing you need to to is to (honestly) estimate your horse’s condition. Type ‘Henneke’s body condition score’ into Google and evaluate your horse yourself. If you do it with an experienced horsey friend (or two) you’re less likely to cheat! Important things to look for are a cresty neck and fat deposits near the dock. A big belly can be a sign of over conditioning, but it can also be what’s commonly termed a ‘hay belly’, or the result of a horse using itself incorrectly so a large belly alone is not a good measure of condition. The Henneke scale can easily be used as a benchmark for horse owners and equine professionals alike to determine if a horse is over or under conditioned, and also to monitor any weight loss or gain.

Effective management strategies are the most important part of treating IR. IR horses should not be allowed access to lush pastures, what’s commonly referred to as ‘premium’ hay or grain-based concentrates. It’s crucial that horses are fed low-sugar/low-starch grass hays and that any high-sugar concentrates (and treats) are eliminated from the diet. Your hay should be analysed for its sugar and starch content and the total percentage of ESC (ethanol soluble carbohydrates) + starch should not exceed 10-12%. You may need to spend some time looking for hay suppliers that will provide an up-to-date pasture analysis. Don’t assume that because the ESC + starch was 11% last year it will be 11% this year.

If the sugar content is unknown or suspected to be high you can work around this by soaking the hay in cold water for 60 minutes or in warm water for 30 minutes immediately prior to feeding to prevent spoilage. The hay must be rinsed and the water discarded where it’s inaccessible to horses who will enjoy lapping up the lolly water. When it’s hot it’s important to discard any uneaten hay prior to it spoiling.

During spring and possibly autumn it is very likely your IR horse should not be allowed onto pasture or only be allowed out between very early morning and late morning as this is when sugars are at their lowest (provided there wasn’t a frost the previous night). Some IR horses can’t be on pasture ever. Grazing muzzles are another great way to prevent excess weight gain in horses at pasture (provided they can cope with the pasture itself) as are well designed ‘paddock paradise’ systems.

If your horse needs to lose weight then it should be fitted with a grazing muzzle and/or be taken off any lush pasture and be provided low sugar hay in slow feeder nets as many times a day as possible at around 1.5%-2% of its body weight per day (including any pasture it has access to). Reducing calorie and sugar intake will aid weight loss, however will not increase insulin sensitivity. To help your horse long-term the ideal outcome is to increase insulin sensitivity. Recent studies have shown that regular brisk exercise will not only cause weight loss, but will result in increased sensitivity to insulin. Hand-walking, lunging, long-reining, driving, riding, ponying and so on are all excellent forms of exercise. Of course you must ensure you don’t exercise your horse if it’s currently suffering from a laminitic episode.

As a side note, it’s important to note that IR is on a scale. This means that some horses will be able to digest a certain amount of sugar and starch with few ill effects while others will take a few mouthfuls of grass have a laminitic episode. However affected your horse or pony is it’s important to implement a calorie controlled, low starch and sugar diet teamed with a good exercise program. If your horse has PPID then it will also need medication such as pergolide and this should be discussed with your vet.

If extra condition is needed then almost all IR horses can be provided beet pulp and a small amount of soybean meal if additional protein is required and most can also have lucerne, copra, lupins or low GI soy-based pellets.

It’s also crucial that horses are getting enough essential vitamins and minerals such as copper, zinc, selenium, magnesium. A good quality, grain-free mineral and vitamin supplement, ideally one that’s developed by an independent nutritionist and not a large commercial feed company, is also required along with a source of omega 3 such as flaxseeds or flaxseed oil salt.

It is not yet known if insulin resistance can be completely prevented, but ensuring a healthy diet for at-risk horses and breeds is crucial. If your horse is on a strict diet and exercise program and is getting a balanced diet and medication if required then it’s very likely to that it can and will lead a normal, healthy life.


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