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What is EMS?

Equine Metabolic Syndrome (EMS) develops when genetic and environmental factors interact in an individual horse or pony. Environmental factors such as grazing on lush pasture, consumption of concentrates, and interference with seasonal weight loss will promote obesity in genetically susceptible horses. Some breeds of horse, such as our native British ponies, are recognised to be genetically susceptible but the condition can occur in many horse breeds.

EMS is characterised in horses and ponies by:

  1. Being overweight and/or having abnormal fat distribution
  2. Insulin resistance
  3. Laminitis

Whilst all horses with EMS will by definition have insulin resistance, not all horses with insulin resistance will have EMS, and nor will all obese horses have insulin resistance.

Obesity is associated with the development of insulin resistance in several species. It is hypothesised that abnormal amounts of fatty tissue may cause insulin resistance through many different mechanisms. In horses insulin resistance may also develop as a result of a diet high in starch and simple sugars.

Signs of EMS

Why is laminitis a characteristic of EMS?

The presence of insulin resistance in patients with EMS is thought to play an important role in their risk of developing laminitis. When horses and ponies with EMS consume large quantities of sugar and starch (such as that found in grass) it results in higher levels of circulating insulin than in an unaffected horse. High levels of insulin have been shown to be a cause of laminitis.1

It should be remembered that grazing on its own is unlikely to cause laminitis if there is no underlying hormonal problem.

Laminitis and EMS

How would I know if my horse had EMS?

If you would like to learn more about recognising obesity in your horses and ponies, watch Dr. Teresa Holland’s fat scoring video on our youtube channel: www.youtube.com/talkaboutlaminitis

EMS diagnosis

How is EMS diagnosed?

EMS can be diagnosed by your veterinary surgeon, and requires dedication to treat. Weight loss is crucial and exercise (once recovered from laminitis) can help insulin receptors to become sensitive to insulin again. Some prescription medications can help EMS cases but only if the strict weight loss and exercise programmes are followed.

It is important to ask your veterinary surgeon for help as they will be able to recommend a suitable programme and can monitor your success with further blood tests.

EMS treatment

How is EMS treated?

  1. Where laminitis is not a limiting factor, daily exercise aids weight loss and improves insulin sensitivity. Exercise intensity does not have to be high, but aim to build up to regular exercise of 30 minutes or more daily once recovery from laminitis is complete. Obtaining and maintaining your horse or pony's correct body weight is vitally important. Ask your vet to show you how to use a weight tape correctly and how to assess body condition score and cresty neck score – this will help you to monitor progress.

  2. Dietary management should reduce both energy intake and non-structural carbohydrates (simple sugars and starches) but changes to your horse or pony’s diet should be made slowly (over the course of at least 2 weeks).

  3. Restriction of grazing using a muzzle or starvation paddock can reduce grass intake while still maintaining exercise obtained during turnout. Simply limiting duration of turnout is unlikely to be successful as horses and ponies are able to consume a large portion of their grass intake in the first 2-3 hours of grazing.

  1. Soaking hay can be a very useful way of reducing the sugar and therefore the calorie content. The length of time you need to soak hay varies considerably between different hays, so it may be worth having a forage analysis done to find out the energy content of your hay. Soaking hay would normally be between 1-12 hours, depending on the type and quality of your hay. When giving soaked hay it is also advisable to feed a broad spectrum multivitamin/mineral and amino acid supplement (ask your vet for advice).

  2. Feeding hay in haylage nets or inside two hay nets (“double netting”) can help slow down your horse or pony to prolong feeding time.

  3. Regular check-ups from your vet will help monitor the response to management changes and any other treatment, and allow assessment of your horse or pony’s insulin levels.

  1. De Laat et al (2010) Equine Veterinary Journal 42 (2) 129-135