Metabolic syndrome, Cushing's disease can both lead to laminitis
For owners of horses that are prone to laminitis, there's a constant balancing act between the kind and amount of hay that can be fed and the amount of exercise they need. Sometimes it's hard to tell what makes a horse lame and miserable with an attack of laminitis.
One of the things that can cause laminitis - an inflammation of the structures inside the hoof - is metabolic syndrome.
Ten years ago there was no defined veterinary term for the condition of ponies and horses who were "easy keepers" - those who were prone to getting fat and who were also at increased risk for getting laminitis and the more serious condition of founder.
Even without a veterinary term though, it was something that vets, farriers and horse owners could recognize, said Dr. Simon Peek, who is with the University of Wisconsin School of Veterinary Medicine.
Peek started his practice in the United Kingdom at Bristol, near Dartmoor National Park, then worked at Cornell University for nine years before taking his position in large animal internal medicine at Madison.
Equine metabolic syndrome was not "discovered" 10 years ago, said Peek, but was a term borrowed from human medicine where it covers people with Type 2 diabetes who are predisposed to cardio-vascular disease and stroke.
The part of that medical package that relates to horses is insulin resistance. The horses who are likely to have metabolic syndrome and laminitis are generally overweight and have abnormalities in their blood lipid profile, he added.
Sometimes mares with "equine metabolic syndrome" or EMS, as vets have agreed to call it, have unusual reproductive cycles. While normal mares do not cycle during winter months, sometimes mares with metabolic syndrome will.
Then during spring and summer these EMS mares can have long intervals between their cycles.
Peek said certain kinds of equines are more susceptible to the problem. Ponies - including the Dartmoors he worked with in England - along with Pasos, Arabians, Saddlebreds and Spanish mustangs are among those breeds that are more likely to have the problem.
"Quarter Horses and Tennessee Walking Horses are less so and it is very rare in Thoroughbreds, Standardbreds and draft horses. It also seems to be rare in donkeys."
One of the reasons vets and horse owners are taking notice of metabolic syndrome is its very strong association with laminitis and founder, conditions that have been "feared ever since people have worked with horses," Peek said.
Laminitis is a condition where the inner structures between the hoof and foot become inflamed, causing pain and lameness. In the worst cases it can progress to founder, where the hoof disconnects from the structure of the foot. Horses can be lost to founder.
People who work with horses have often recognized "spring grass founder" when horses or ponies get a huge dose of lush grass and end up lame or foundered. "A lot of those horses and ponies have equine metabolic syndrome or EMS," Peek said.
Anytime there is an unexplained instance of laminitis, horse owners and veterinarians should consider the possibility that it was caused by EMS.
Horses or ponies who are "easy keepers" - those that don't take too many calories to keep the flesh on - may have EMS. "Some are obese by the age of three, four or five years of age. Often these equines have their first onset of laminitis from age five-15."
There are some laboratory tests that can be used to help diagnose EMS but generally it can be done with a physical exam and a good history on the horse, Peek said.
He advised horse owners to get into the habit of doing a body condition score on their horse and if those scores get truly high - meaning the animal is quite fat - that could spell danger for laminitis.
"It doesn't require a trip from the vet. You can learn to do the body condition score and then do it often."
Some horse owners may want to take radiographs of the feet to use as a baseline of comparison in case the horse has problems later. Some founders can get so bad that the coffin bone inside the hoof rotates and punctures through the sole of the hoof.
Unlike the similar metabolic syndrome in humans, EMS often doesn't result in elevated blood glucose levels, however insulin levels are generally elevated. Peek warned that it's important not to try to do blood tests when the horse is actively painful.
The normal response to stress will elevate blood glucose and insulin levels, meaning tests done during an acute episode will not yield very useful results.
"There are some fancier tests with glucose challenges and several university groups are looking at how to diagnose this better."
One of the warning signs to look for in diagnosing EMS is abnormal fat, including a lot of fat in the top (crest) of the neck. Fat over the ribs and hips is also often present in EMS horses and ponies.
However, a fat horse can also be caused by Cushing's disease. These horses are generally older and when this disease is present it will often give the horse a shaggy coat that doesn't shed easily in the springtime.
Peek said Cushing's horses drink more water, urinate more and are subject to muscle atrophy (wasting) as time goes by. They can also be prone to laminitis.
When it comes to treating the EMS horse or pony, he said there are some research projects testing human drugs like metformin and levothyroxine. "They are largely unproven now but the trials continue."
For horses or ponies that are prone to laminitis, Peek said a good farrier is worth his or her weight in gold. "A farrier is of more use to you than the veterinarian. You really do need an excellent farrier."
What the laminitic or foundered horse needs after its feet start to feel better again is exercise. "They should have a minimum of two or three hours per week and more is even better."
Peek said that often the hardest thing to get horse owners to buy into with these horses is to keep them off pasture for the rest of their lives. "It seems so unfair and cruel to many people and it is more expensive, but if a horse or pony has EMS then pasture is in their past."
These equines will need to be fed hay and it should be grass - never alfalfa. It should be fed at the rate of 1 ½ percent of their body weight, he said.
The hay should be tested and analyzed to find out what kind of carbohydrates and sugars are in it. Regardless of the test, these kinds of horses should never be fed their hay on a free-choice basis.
"Horses will voluntarily consume 5 percent of their body weight and that's three-four times the amount of hay they should get."
There are a number of feed supplements on the market to try to treat EMS horses. Many of them incorporate chromium and magnesium; some are based on herbs and spices like cinnamon and chaste berry.
Some of these treatments are based on human research and some are based on folklore. "There is not yet proof that any of them work," said Peek.
One of the sure-fire ways to reduce the carbohydrates in the hay is to soak it in water for six-eight hours before feeding it to the EMS horse. "The hotter carbohydrates will come off in the water."
Like a diabetic human, horses whose carbohydrates are being restricted can lose too much weight and get too thin. Peek suggested feeds like rice bran and beet pulp to which corn oil can be added to put more calories in the horse's diet without adding carbohydrates.
Peek said that in the next decade or so the active areas of research will concentrate on improving glucose metabolism and veterinary medicine may have better answers for these horses.
Peek spoke to horse owners as part of a client-appreciation program for clients of Lodi Veterinary Care and Madison Equine recently.
For more information he suggested the following websites - The American Association of Equine Practitioners - www.aaep.org
or the one for the American College of Veterinary Internal Medicine at www.acvim.org.