Management of the Insulin Resistant Horse

Equine insulin resistance is now the #1 cause of laminitis in the world.  New studies, from the Universities of Kentucky and Virginia, suggest that half of the horse population is overweight and insulin resistance is a probable, normal event in geriatric horses. With proper care, these horses can live full, productive and happy lives.

Insulin resistance is common in older people and appears to be a normal event in the ageing process of horses too.  Due to muscle loss, lowered exercise, and increased fat, insulin levels go up in many older horses. Although insulin resistance is seen in geriatric horses with or without Cushing ’s disease, older horses should have insulin and ACTH testing as they age in order to avoid laminitis events.

NEW TESTING PROTOCOLS

In the past (even one year ago) horses were misdiagnosed with normal insulin, when in fact, they were insulin resistant. Since 2012, the new standard way to ensure proper evaluation of insulin in a specific horse is the Oral Glucose Insulin Response Test.

On the day of the test, Karo light syrup is squirted into the mouth at a rate of 7cc/100 pounds body weight (70cc in a 1000 pound horse), in the morning after a night of hay eating.  Blood is pulled 1 hour after the challenge. It is then spun, harvested and sent on ice to the lab via express mail. 

Because we already know the insulin response in normal horses, we can easily confirm insulin resistance in the horse with this new test. This allows owners to institute programs to help lower insulin and retest blood levels every year for follow up monitoring.

CONTROLLED FEEDING

The key to the equine insulin resistant diet is to control carbohydrate metabolism by eating the right foods in the proper amounts. Your horse ideally will get some fresh grass, hay, grain, and snacks. Often the scenario is the horse gets too much of one item, causing a laminitis trigger.

Forage is the basis of the horse’s diet.  Horses are designed as continual slow eaters and long periods of no or little food lead to huge insulin surging.  Hay eating should be slow and steady 24/7 to stabilize insulin levels. Slow feeder hay systems can help since many insulin resistant horses tend to gobble hay.  Many commercial small mesh hay nets have holes that are too big. Nets that are designed as slow feeders can more effectively control hay intake. A horse 500-1000 pounds needs a net with 1.5 x 1.5-inch holes and a pony less than 500 pounds usually needs a net with 1x1-inch holes to ensure long, slow eating.  Hay testing can be helpful in monitoring sugar intake. 

An all-hay diet will lead to problems due to vitamin/micro nutrient deficiency. If you hear that the solution to laminitis in an insulin resistant horse is to keep it on a dirt lot and feed it only hay, you are getting inadequate and incorrect information. A low non-structural carbohydrate (NSC) pellet feed will provide vitamins/micro nutrients and a high amount of protein.

Pasture turnout has multiple advantages in keeping your horse healthy. Exercise helps build muscle and increases circulation to the feet.  Both of these can help in lowering insulin levels. While grass turnout ensures horse exercise, intake should be monitored. Blood testing insulin while on grass is a way to see if intake is at a safe level.

Did You Know?

• The sun in the afternoon can double sugar levels in a field 
• Fields should be cut no lower than 4-6 inches. Short “golf course” like fields have more sugar.
• Rye seeds, common in commercial pre-made “pasture mix” blends, have a higher sugar content
• A weedy field has a high concentration of iron leading to elevated insulin

Grazing muzzles can be used to slow the intake of grass. Horses take in 3-4 pounds of grass per hour, and a muzzled horse turned out 4 hours a day will consume 240 pounds less grass a month.

A WORD ON SUPPLEMENTS

No hay is balanced; it varies from cutting to cutting and in nutritional content due to storage. Ration balancers, concentrated controlled starch supplements, can be added to help support the nutritional needs of horses with metabolic disturbances. The high-quality protein supports muscle development and maintenance, helps with hoof quality, and slows the exit of food out of the stomach so horses feel fuller longer and are not frantic about eating.

Giving snacks are a fun part of owning a horse but many horse cookies, nibblers, and commercial products are very high in carbohydrates and need to be avoided.  Sugar-free peppermints, peanuts in the shell, cut up hay cubes, alfalfa or timothy pellets, and even celery are great low carb snacks to give horses.

There are many supplements on the market for Insulin Resistant horses, but it is important that owners know the sugar/starch content prior to giving.  If you have a horse with insulin issues, you cannot blindly add supplements without knowing if they may be high sugar.  In addition, there should be a track record showing horses do have improved insulin numbers.

FARRIER CARE

Farriers are often the first line of defense against insulin resistance laminitis and the key to early detection. Because they see the hoof regularly, they can pick up changes or notice a lameness on visits. They are a major part of the team and should be consulted regularly on blood tests and radiographs to ensure the long-term comfort of your horse.

Your Farrier has important experience with the hoof which is vital in knowing what has or has not worked in the past and will notice signs of possible insulin resistance such as:

• Overly sensitive response as they put nails in – the horse flinches more than in the past
• Laminitis with no known cause
• Sore-footed more in the winter

During a laminitis attack, your farrier will help protect your horse’s feet by trimming more frequently, using thin sole pads or glue-on shoes, and requesting radiographs for closer monitoring. If your horse is sore after routine trims, you do not need a new farrier, you need to get the horse tested.

IN SUM

Older horses should have Insulin and ACTH testing as they age in order to avoid laminitis events. With proper testing, a thoughtful feed program and good farrier care, your insulin resistant horse can lead a productive and comfortable life. Go to http://youtu.be/wLkO4Ss3T3w?list=UU-dmsjT3vfJAu0SVQr02RJw Dr. Reilly preform an IR test on a pony.

Dr. Frank Reilly has been in equine practice for 27 years. He is a member of the American Veterinary Medical Association, the American Association of Equine Practitioners and a veterinary member of the American Association of Professional Farriers. He has spoken on equine insulin resistance/laminitis throughout the USA, including at the International Laminitis Conference and International Hoof Summit.

www.equinemedsurg.com

caption: A pony with a cresty neck is