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Equine obesity is no longer someone else’s problem. Between 30 and 50% of UK horses are now thought to be overweight, with the figure standing at more than 70% in some native breeds. Many yards will be home to a horse on the worrying side of well-covered, with an increased risk of health complications and associated diseases ranging from poor performance to laminitis — one of the most common reasons for euthanasia.

While equine obesity emerged as a welfare issue some years ago, the number of overweight horses continues to rise. Experts from the UK veterinary world gathered recently to discuss this growing problem, combining their knowledge with the latest research results to create the most up-to-date picture yet of the state of our horses’ health.

Here are the key findings:

Fact 1: Being overweight is unhealthy

The accumulation of body fat is a normal physiological response to a positive energy balance, when calories taken in exceed those burned off. The report defines obesity as the excessive accumulation of fat to the point at which there is a negative health impact.

Health issues related to obesity include inflammation, the metabolic disorder hyperlipaemia, vascular dysfunction (problems with vessels, such as veins) and potentially harmful cell activity known as oxidative stress. While laminitis is typically considered a risk for fat ponies, excess weight will leave any horse prone to equine metabolic syndrome (EMS) and subsequent laminitis.

Add to this the possibility of impaired athletic and reproductive performance, susceptibility to some forms of colic, thermal stress (overheating) and excessive joint loading, and it’s clear that every extra pound contributes to a weighty problem.

Fact 2: Fat takes many forms

Fat deposits may be generalised (widespread) or concentrated in certain areas such as the crest of the neck. External fat may be stored under the skin and felt easily with the fingers, while internal fat — the adipose tissue that can accumulate around organs and muscle — is more covert, or hidden.

A horse with a body condition score of seven or more on a nine-point scale is considered obese, with fat likely to account for more than 20% of his bodyweight.

Fact 3: Active horses can be obese

Like humans, many horses have inactive lifestyles: the companion animal is the obvious candidate. The root of the problem is too much food and too little exercise. It is noted that owners of leisure horses in particular tend to feel that their animals are working hard when, in reality, their exertions have minimal impact on their energy requirements.

The report contains some surprising statistics, however. While horses used for pleasure riding are more likely to be overweight, one study revealed that the prevalence of obesity in competition horses also appears to be high — with show and dressage horses typically at the heavier end of the scale. Because the fuller figure is becoming the norm, it appears that many of us have lost the ability to visually identify an overweight horse.

Fact 4: Measurements may vary

The report highlights the need for an accurate means of assessing weight and monitoring responses to dietary changes.

Every system has its pros and cons. Weigh tapes used around the girth take no account of fat that accumulates in other areas, for example, or the fact that changes in girth circumference will lag behind more general changes in bodyweight. Body condition scoring has its uses but is considered a crude and subjective means of assessing obesity.

Measurement of the belly girth (running a tape measure around the widest point of the abdomen) is a more sensitive indicator of generalised fat loss, but experts agree that a calibrated portable weighbridge is the most effective method of monitoring weight.

While there are no laboratory tests that can reliably pinpoint when adiposity (internal fat) starts to damage health, tests for insulin dysregulation can identify EMS and the associated risk of laminitis. Horses that are apparently lean but suffer insulin dysregulation or laminitis should undergo ultrasound assessment to assess internal fat deposits.

Fact 5: Weight-loss programmes can work

A horse identified as too heavy should ideally start a gradual but consistent programme of weight loss. A reduction of 0.5-1% of bodyweight per week is considered a realistic target, achieved through a tailored diet balancing calories with exercise.

The report includes detailed recommendations about grass and hay intake, outlining the benefits of soaking hay and weighing every meal. Most owners feed their horses far more than they need to stay healthy — a leisure horse requires just 2% of his bodyweight in forage per day.

One problem is how to restrict grazing, especially among the native ponies and cob types that are typically field-kept and most prone to obesity issues. Horses were designed to forage long distances over barren pasture rather than graze all day on lush grass, so grazing muzzles and non-grass turnout are key.

Medical treatment should not be a substitute for appropriate management and diet, the report authors feel, and is only necessary in a small number of obese horses.

Fact 6: Management must be ongoing

The vets point out that once a target weight is achieved, an appropriate lifestyle must be maintained if the horse is not to return to his former obese condition.

Achieving an appropriate weight does not guarantee improved insulin sensitivity and an end to the threat of laminitis. The message is clear: once a horse has been overweight, he may always be at risk.

Successful management should be based around the normal cycle of weight loss and gain over a calendar year. If a horse has excessive body condition at the end of summer, his owner should aim for corrective weight loss over the winter.

Fact 7: Horse and owner need support

The report emphasises the need to consider the horse’s welfare as he loses weight. Owners are advised to avoid exposing a horse to trigger factors for eating, such as stress, boredom, or the sight of food or empty feed buckets, and to provide distractions in the form of exercise, environmental stimulation and interaction with humans or other horses.

Peer pressure is an obstacle: an owner’s attempts to slim down a horse are often undermined by others with little knowledge of appropriate bodyweight.

Success is most likely when an owner has the full support of everyone at the yard.

Fact 8: Radical change is required

To reduce levels of obesity, the report authors recommend a robust and united approach. Societies for those breeds most likely to become obese in modern management systems must be proactive in informing their members, while governing authorities in the showing world should implement “radical change” to ensure that fit and athletic horses are celebrated over obese animals.

Wider education should be focused on issues such as the perception of how a horse of an ideal weight looks and how little most need to be fed to maintain a healthy body condition.

Ref Horse & Hound; 16 August 2018