Most equestrians would agree that an obese horse is an unhealthy horse, and yet one study found that up to 70% of horses could be considered overweight. Part of the problem might be to do with the inherent difficulty associated with body condition assessment. So how can you tell?

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The difficulty in deciding

Distinguishing fat deposits from muscle development isn’t always easy, and then there’s the complicating factor of season dependent weight fluctuation. It is typical for wild horses to bulk up in late summer when grass is abundant and highly nutritious. Going into winter with a little extra covering is one of nature’s useful mechanisms, helping horses through tougher months when food is scarce and temperatures plummet. Domestic horses are not so different from their wild counterparts; to an extent their constitution is built to undergo the same weight changes and expect a ‘starvation’ phase. 

The trouble is that owners might be shocked by changes to their horse’s shape and might consider them to have “wintered poorly”. In trying to ensure that a horse “comes out of winter well” they may be over-rugged and overfed the following year. Overfeeding can be easy to achieve, as during this starvation phase the body makes the absolute most of every calorie eaten.

There are, of course, complicating factors when we consider how many horses are worked and competed year-round. And these guys need the correct balance of food in order to carry out said activity. So, we see that the issue is complex. What’s more, the natural tendency for a horse’s weight to fluctuate doesn’t mean we should allow them to overeat and under-exercise throughout the summer months. What we know for sure is that obesity in equines has very real consequences for their health. Here we review some obesity related conditions as well as how to tell if your horse is indeed a healthy weight or not.

Health conditions and the obese horse

Laminitis

Laminitis is one of the leading reasons for euthanasia in horses. Within the horse’s hoof, laminae (folds of sensitive tissue) fill the space between the hoof’s outer horn and other structures such as the pedal bone. During laminitis the blood supply to these laminae is interrupted and as is transportation of oxygen and other nutrients vital for tissue health. Inflammation results, along with degradation of the tissue and in turn the structural integrity of the laminae deteriorates.

In a healthy hoof, the laminae support the pedal bone (and therefore the horse’s bodyweight). However in laminitic cases this can rotate downwards, causing severe pain when mobilising. In severe cases, protrusion through the hoof is even possible. The pain associated is severe. The classic stance of the laminitic is one who leans back onto their hind hooves in order to take the weight off painful front hooves. However, laminitis can affect all or any of the four feet.

Obesity is one of the leading causes of laminitis as it alters the metabolism of the laminae, leading to mechanical failure.

Osteoarthritis

Osteoarthritis refers to the degradation of the cartilage covering the bone ends within synovial joints. As this cartilage roughens and wears away, pain and inflammation within the joint ensues. Carrying excess weight, as with obesity, puts additional pressure on these joints exacerbating the pain. Maintaining a healthy weight is one of the simplest and most beneficial things owners can do for an arthritic animal.

Heart disease

A recent study found that obesity causes some marked changes to the equine heart; similar in some ways to that on the human heart. One example of many, is that obese horses were found to have fat tissue infiltrating the heart muscle. It is easy to see how this might reduce muscle contractility within the heart; and therefore the efficiency of circulating blood around the body. The study concluded that the effects of obesity on the horse’s heart are likely not only to diminish the horse’s ability to exercise but may shorten their lifespan as well.

Insulin resistance

Insulin is required to help transport glucose from the blood into tissues. It is then utilised for energy. Insulin resistant horses usually produce excess insulin in response to the ingestion of glucose. Obesity is a predisposing factor for the latter. A vicious cycle develops as they become increasingly desensitised to insulin and therefore the body demands more and more insulin to be produced. This disruption in the processing of glucose renders a horse hyperglycaemic. This raised blood glucose affects blood-flow, and we already know that reduced circulation predisposes a horse to laminitis.

Identifying obesity in horses

Body condition scoring

These systems of body condition assessment are visual and, although a little subjective, are perhaps the most helpful tool we have currently. The Blue Cross use a version which assesses characteristics such as fat palpable over bony areas, the shape of the neck, prominence of backbone and pelvis, shape of rump, size of thigh gap and angle of cavity behind the tail. They work on a scale of 0 – 5; horses scoring 0 are likely to be barely alive and those scoring 5 to be morbidly obese.

What does a score 3 horse look like?

A horse of ideal body condition is described as having some fat palpable beneath the skin, neck muscles which are not starkly defined, and as having a neck which flows gently into the shoulders without obvious interruption. The withers are “rounded”, and the back is either smooth or forms a slight ridge. The ribcage should be easily palpable but not visually obvious. The hind quarters should be nicely rounded and the hip bones just visible. 

For a more in-depth look at the body condition scoring chart, take a look at the  BEVA Horse Body Condition Chart 

Should you believe your horse to be either over or underweight, it is helpful to view the entire scale and compare them to each of the pictures.

What do I do about a fat horse?

Firstly, it is important not to starve a horse for quick results. This can cause all sorts of health problems including gastric ulcers, especially where restricting forage is concerned. Slow and steady changes are safer, kinder, and usually reap longer-lasting results. Making a plan with your vet to include dietary changes and exercise regimes (where possible) is by far the best way to approach the situation.

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