Fat horses and ponies, laminitis and the equine metabolic syndrome

horseWe all know of fat cresty-necked ponies and horses that are prone to laminitis (tender feet or founder). It’s a very common problem and many affected animals develop a condition called Equine Metabolic Syndrome (EMS).

EMS is a complicated disorder of metabolism with a lot of similarities to human type 2 diabetes. Both are basically insulin-resistant states in which chronic inflammation develops. However whereas in human type 2 diabetes inflammation affects mainly the arteries, in horses and ponies it affects the laminae (the tender lining of the feet inside the hoof), causing painful laminitis.

While EMS is much more common in ponies, it can also develop in standardbreds, warmbloods and quarter horses. It’s not common in thoroughbreds. Males and females are equally susceptible.

Where the term ‘horses’ is used in this article, it includes ponies.

Diagnosis

EMS is diagnosed when all three of these signs are present:

  • obesity and/or fatty deposits e.g. a cresty neck (or a history of this in the past). There may be a fatty layer over the ribs and over the top line to the tail head. Geldings may have increased fat around their prepuce whereas mares may have increased fat around their udder.
  • laminitis or a history of laminitis, or transverse hoof rings that indicate previous bouts of laminitis
  • insulin resistance diagnosed on blood testing carried out by a vet

Note that obesity and a cresty neck are not sufficient for a diagnosis, blood tests are needed for confirmation.

Treatment

EMS is tackled in three ways – diet/weight loss, exercise and medication.
In addition the feet must be trimmed regularly by a good farrier.

If the horse is not lame, diet restriction and an exercise regime alone may be enough to return it to a normal weight and manage the problem successfully. In all other cases it is important to consult a vet at the outset.

Diet and weight loss

Diet restriction has to be carefully managed. If food is restricted too much, especially in very fat horses, hyperlipaemia (fat in the blood) can develop. This is a serious complication. The aim should be to provide a diet low in sugars and starches, and this is where veterinary guidance is invaluable.

Restricting the diet is difficult for the caring owner, but it shouldn’t mean starvation. The horse should be taken off pasture (which can have high sugar levels) and fed a measured amount of soaked meadow hay in small lots during the day, perhaps spread out over dry ground to give it some exercise as it browses.

First get baseline measurements of your horse’s girth (using a weight band) and neck circumference so that you can chart weight loss.

Offer the horse 2% of its current bodyweight in fresh meadow hay that is then soaked for 60 minutes in cold water or 30 minutes in warm water to reduce its water-soluble sugar content. (If the hay has been tested and has less than 10% non-structural carbohydrates i.e. starches and sugars, then it can be fed dry at 1.5% of current bodyweight.) Offer the hay in at least two lots during the day.

Supplements should be given to add vitamins and minerals that are lost during soaking but that are needed for the repair of damaged feet.

Exercise

A committed exercise programme is important but this should not be undertaken if the horse has tender feet. If it isn’t lame it could be ridden or lunged about five times a week building up to 20 to 30 minutes a session. Just turning the horse out doesn’t seem to be as effective in managing insulin resistance problems as organised exercise.

If the horse has painful feet, it shouldn’t be exercised at all until it is no longer lame and is off any anti-inflammatories that your vet might have prescribed. Enforced exercise stresses already weakened lamina attachments and causes more damage and inflammation. Restrict the area the horse is in and have it on soft bedding or ground to limit this trauma.

Weight reduction should be documented by scale weight or weight tapes, and neck thickness and diameter can be monitored over time.

Medication

There is reasonably priced medication that can be prescribed by your vet. It is given by mouth to manage EMS by decreasing both blood glucose levels and corresponding insulin spikes after feeding. Recent research suggests that it may be appropriate to start this treatment straight away.

Prevention

Prevention of EMS should focus on maintaining a healthy body condition score and normal body weight while ensuring regular exercise. This is particularly important for high-risk types of horse, because they are more efficient users of calories than others.

Susceptible horses will need careful management throughout their lives to prevent recurrence.

Note

It’s been suggested that the reason some horses are particularly susceptible to EMS is that they have the ‘thrifty gene’ that enabled their ancestors to survive in harsh environments where they evolved to put on weight in summer and lose it in winter. Their increased efficiency of energy metabolism has become a liability in modern environments where there is plenty of nutrient-rich pasture and feed, so they are not allowed to lose weight during winter. They tend to stay fat all year round.

So it’s up to us, caring owners, to manage the body condition and exercise regimes of our horses to prevent distressing problems like EMS.

by Marjorie Orr, retired veterinarian and lifestyle farmer
and Michelle Logan, equine medicine specialist

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