Equine Metabolic Syndrome (EMS) in Horses

Excess weight and fat

The biggest risk factor is obesity. Hormones produced by excess fat cells affect the body's ability to respond to insulin, so the body produces more of it. Fatter horses are therefore more likely to release more insulin, which makes them more prone to laminitis.

Genetics and breed

Native pony and cob breeds are anecdotally considered particularly susceptible, and published cases largely involve British native breeds. Horses with EMS are often called "good doers" or "easy keepers". The genes behind this are likely to have helped survival in times of famine.

Diet

Insulin is released in response to what a horse eats. Higher-sugar diets cause more insulin to be released and raise laminitis risk.

Hay is simply dried grass, so it can also be high in sugar. Hay is not automatically "safe" for a horse with insulin problems.

Inactivity and age

EMS appears to be more common in physically inactive animals, and insulin levels are generally higher in older horses and ponies. A UK study of native ponies and cobs linked EMS to age, being female, a more sedentary main activity and obesity.

Not only overweight horses

A horse does not have to be overweight to have EMS. Research at the Royal Veterinary College (RVC) found insulin dysregulation in ponies of many body conditions, ages and exercise levels. It also found that looking at a pony alone is not a wholly accurate predictor.

Weight management comes first

The primary treatment for EMS is weight management agreed with your vet. EMS is controlled mainly by diet and exercise aimed at improving how the body handles insulin and reducing obesity. This is a long-term strategy that needs diligence.

Feeding for weight loss should be high-fibre and forage-based. It should be done under veterinary supervision, with regular weighing and fat scoring. Our guide to Is My Horse Overweight? explains hands-on scoring.

Feeding without crash dieting

Never put a horse on a crash diet. Horses need a steady supply of food, so the aim is to reduce calories without cutting the amount of forage. Long gaps without food can cause stomach ulcers and behaviour problems, and small-holed haynets can slow eating down.

Redwings does not recommend "starvation paddocks", because the newest grass growth is always high in sugar. It suggests strip grazing or a grazing muzzle as options between May and September, although strip grazing must still allow exercise.

Consider everything that goes into your horse's mouth, including treats, apples and carrots. Weigh feeds, including hay. Your vet or a nutritionist can tailor the plan, including whether hay should be soaked or analysed.

Exercise and rugs

Regular exercise is a key part of a weight-loss programme. It can be built up gradually, starting with more time spent walking. The RVC found insulin dysregulation was less common in ponies that did more exercise.

If your horse has laminitis, follow your vet's advice on exercise. It is also worth asking whether your horse really needs a rug, as rugs may reduce natural insulation and contribute to weight gain.

Medicines, passports and competition

In some cases medicine may help. World Horse Welfare says newer weight-loss medicines exist, but they are not without risk. They should be used only where the risk of laminitis outweighs the risk of the medicine, or where diet and management have not been enough. Talk to your vet.

In the UK, horses are classed as food-producing animals, and the passport declaration decides which medicines can be given. Your vet must ask to see the passport if they do not already know its status. Some medicines are for non-food horses only, and signing a horse out of the food chain is irreversible. If you compete, most medicines are prohibited if detected at the time of competition, so keep dated records and ask your vet.

Monitoring over time

All horses with EMS must be monitored frequently for the earliest signs of laminitis. A European vets' consensus suggests a re-check ideally every 6 to 12 months. A weighbridge is ideal for tracking weight, although weigh tapes and apps are useful alternatives. Tapes are not 100% accurate, but they detect change.

Owners of overweight horses often underestimate their horse's condition. EMS horses are also often resistant to weight loss, which can be upsetting, so support from professionals, friends or yard mates can help.