Equine Metabolic Syndrome (EMS) – The Easy Keeper Disease

By Garrett Metcalf

It is that time of year when cases in veterinary practices that are diagnosed with EMS or Equine Metabolic Syndrome spike. The reason cases of EMS spike are because the fast growth that pastures experience in the spring. Before EMS was well understood or discovered, many of these horses were diagnosed with grass founder, but through research the process of the disease is now better understood. The disease is caused by obese overfed horses and breeds of horses that have “hardy genes.” These are breeds that generally need less caloric intake to meet their daily energy needs. Although some breeds are at higher risk such as ponies, just about any breed can develop EMS.

Risk Factors for EMS

The key risk factor for development of EMS is weight gain, breed, high caloric intake and very little or inconsistent exercise. Horses that gain weight easily on pasture turn out or are getting too many calories from grains plus hay can be put at risk of EMS. Increasing levels of obesity in horses causes insulin resistance just like in humans, but fortunately for the horse, they have a very robust pancreas that is able to keep up with the extra demand for insulin to provide adequate amounts of glucose to tissue and organ systems despite the insulin resistance. This overproduction of insulin in order to keep up with the resistance causes a very key clinical sign of laminitis, which can be the most debilitating and difficult consequence of EMS. Over 90% of horses will present for laminitis as the first clinical sign of EMS. Unfortunately, the clinical signs for laminitis can go undetected for many months or even years in some cases until the progression of the laminitis reaches a very severe tipping point. It is not uncommon that horses with this disease go undetected for variable periods of time and have x-rays to prove it. Many times, horses will have rotation of the coffin bone in the hoof capsule upwards of 10 degrees before the horse is lame enough to alert their owners that there is a serious problem. It doesn’t seem possible that a horse can get that bad overnight, but rather in many cases they have mini laminitic episodes that are almost silent to many owners that lead to this much damage to their feet over time.

Identifying Horses at Risk

A common feature that puts horses at risk that owners can detect and address themselves before a laminitic crisis occurs is adipose deposited in certain areas of the horse’s body called regional adiposity. Regional adiposity describes fat or adipose tissue that is deposited in different regions of horses that owners should watch for if their horse is gaining weight. These common areas are the neck, commonly referred to as cresty necks, around the tail head, and sheaths of geldings or stallions. If these areas are noticed to be enlarging, especially in the spring when there is an abundance of fresh grass to graze on plus weight gain, then steps need to be taken to prevent the development of EMS.

Managing an Easy Keeper

It is very common to hear owners and veterinarians refer to heavy horses as easy keepers, but there can be some serious consequences of ignoring or brushing it off as just an easy keeper horse. Simple steps can be taken to reverse or reduce the risk of horses developing EMS by decreasing daily caloric intake. First, it is recommended to remove all grain from a horse’s diet including treats. Drastically reducing turn out time to graze especially fast growing lush grass is absolutely necessary in horses at risk of grass founder caused by EMS. There is some conflicting evidence as to when is the best time of day to allow a horse to graze that is sensitive to high sugars in lush growing grass. Some research has found that sugar levels peek later in the afternoon because of an abundance of sunshine and fully ramped up photosynthesis process that occurs in the grass. It is suggested then if grazing is allowed or deemed safe, that morning grazing is a safer time, but sometimes letting an at-risk horse graze is not worth the consequences. Other methods of allowing safe grazing are to mow the grass very short to minimize the volume of grass intake in a given period of time. If mowing is not an option, specially designed grazing muzzles allow pasture turn out but restrict the amount of grass taken in through the muzzle. Do not worry, as many horses are very quick to figure out how to get grass through the small hole in the muzzle and also allow the intake of water. It is recommended to have a leather poll strap on their halters to prevent injury when turned out while wearing a halter. Dry lot management is sometimes the only option, especially in horses that already have EMS. Keeping a horse on dry lot with no access to fresh grass and feeding more mature hay is sometimes needed to manage more severe cases. There are no current medications to help reduced the effects of insulin resistance due to obesity in horses, but some medications can be used to help with weight loss such as Thryo-L (levothyroxine) combined with consistent exercise.

Laminitis

Laminitis is the most debilitating and painful outcome of EMS, not to mention life threating. It is also the most expensive and difficult aspect of managing a horse with EMS. In order to properly manage laminitis caused by EMS, the horse needs to be examined by a veterinarian, radiographs need to be taken of the feet to assess the severity of the laminitis and an experienced farrier needs to be heavily involved with the management of the feet. If the disease is caught early, proper trimming may be all that is needed plus the other management aspects employed, of course, but in many cases corrective therapeutic shoeing is required. Pain management is another key aspect of addressing laminitis. NSAIDs or non-steroidal anti-inflammatory drugs, opioids, aspirin and an anticonvulsant drug called Gabapentin can help block or reduce pain of laminitis that horses experience. Some of these drugs do carry a risk of serious side effects so careful monitoring and proper dosages need to be on the order of a veterinarian to minimize the risk of side effects.

It cannot be repeated enough that the best cure for disease is through prevention. Taking early appropriate steps to keep horses from developing EMS is by far the best way to prevent the disease from occurring. If there is concern your horse is at risk of EMS, please talk to your veterinarian to determine if management and diet changes need to be made to prevent the development of this disease.