Some ponies and some horses too seem to live on the smell of an oily rag!  How can they eat so little and stay so fat, and why are they so prone to developing laminitis?

Recent studies show that a condition called Equine Metabolic Syndrome may be responsible for the fat pony and laminitis problem.

  • In the wild, ponies are programmed to put on weight during summer and autumn when there is plenty of pasture and fat is laid down.
  • The fat is used up in winter to provide energy when pasture is scarce. 
  • In horses and ponies, most of the fat is laid down in the abdomen which is called omental fat.
  • The omental fat has recently been found to produce hormones.  This help regulates a number of body processes and is programmed toward enhancing ponies' ability to survive long cold hungry winters.  The fat also produces cortisol, a steroid that inhibits the action of insulin, so high cortisol levels result in high blood sugar levels. 
  • In the wild pony, there are evolutionary advantages in this, because insulin inhibition means that blood glucose levels are maintained for essential functions like brain activity at the expense of non-essential tissues like muscle. 
  • As the pony gradually loses weight during the winter, the level of omental fat reduces and the state of insulin resistance becomes reversed.
  • Then in spring the pony is in lean but healthy condition and is ready to indulge safely in the pleasures of rich grazing.

Unfortunately, our ponies tend to go into winter fat, we feed them grain-based feeds or even just hay and other forages, so they don’t lose weight over winter.  This means their insulin resistance is not reversed.  They are sitting ducks for laminitis when the flush of spring grass comes away because their high levels of cortisol and sugar increase the risk of laminitis developing.

This condition is an equine metabolic syndrome or EMS, and it’s seen in ponies and warm-bloods usually from 5 to 15 years of age, although it often occurs in older animals too.

Common signs of EMS

  • Obese adult pony or horse (although a minority may be normal-sized)
  • "Good doer" who puts on weight easily and loses it with great difficulty
  • Ravenously hungry all the time
  • Urinating frequently
  • Lethargic and lazy
  • Infertile or abnormal cycles in mares
  • Abnormal body fat distribution, e.g. thickened, cresty neck; excess fat around the head of tail; fatty shoulders; flabby, fatty sheath; pot-bellied look

EMS can lead to laminitis.  This can be very subtle, with abnormal hoof growth; laminitic rings on the hoof wall, and expansion of the white line with no apparent lameness.  Or it can be obvious, as in the horse or pony that is reluctant to move because of pain in its front feet.  It may stand rocked back so that most of its weight is on its hind feet, or it may spend a lot of time lying down. 

When the signs get worse, you must take the pony off feed, stand it in a yard and consult your veterinarian right away.  Don’t starve it as this can do more harm than good.  Offer a little hay and plenty of water.  There is no treatment as such, but careful trimming of the hooves can help and your vet can advise on how to alleviate the pain.

How can you prevent EMS?

To prevent EMS, control your horse’s diet.  Mature horses that are in ideal body condition and in light work may need little more than good quality pasture or hay and possibly a complete vitamin and mineral supplement.  This ration though simple is low in starch, and this is an important step in avoiding equine metabolic syndrome.

Mature ponies and many horses that are overweight are candidates for equine metabolic syndrome. 

By far the most important aspect of controlling EMS and preventing laminitis in overweight horses and ponies is diet management as follows:

  • They should not be given grain, food mixes with molasses, or unlimited access to pasture.  If they require additional energy, non-starch alternatives such as non-molassed sugar beet can be fed.
  • Avoid sweet treats, even succulents like apples and carrots.  (Sorry - this will be bad news for some of you!)   
  • A little lucerne hay can be used to add interest to the meadow hay.
  • A good mineral supplement will help ensure that the diet contains enough vital nutrients.

Exercise is also essential:

  • Exercise encourages a loss in omental fat, and it also promotes an increase in glucose uptake.  
  • A fit pony (even if slightly overweight) has increased sensitivity to insulin and will lose weight faster than an unfit pony.
  • The exercise must be tailored to the abilities of the animal.  Vigorous exercise is obviously not sensible for very old or stiff animals or those that already have laminitis.