by Dr. Tom Lenz • courtesy of AAEP

Fat horses are at greater risk for exercise intolerance, founder, metabolic syndrome, insulin resistance, the formation of colic-causing lipomas (fat tumors in the abdomen), joint and bone problems, reduced reproduction efficiency and increased stress on their heart and lungs.

According to a recent survey conducted by the Virginia-Maryland Regional College of Veterinary Medicine, 51 percent of the horses had a body condition score (BCS) of greater than 6, which would be considered fat. Nineteen percent of that 50 percent had a BCS of 8-9, which would be considered obese.  Ideally, we would like to see our horses with a BCS of somewhere between 4 and 6.

One reason we are seeing more fat horses today is that horses evolved as free-roaming grazers on sparse pasture types. They gained weight during the summer grazing and lost weight, sometimes several hundred pounds, during the winter.

Once domesticated, horses served primarily as work animals, providing either transportation or draft power that required a tremendous amount of energy in the form of grain supplement. It was not uncommon for cavalry horses to be ridden 30 to 50 miles a day.

Today, most horses are recreational horses and being ridden for a few hours a week. Even show and ranch horses are only worked moderately. In addition, today we fortify our pastures with the goal of improving weight gain and productivity of cattle and other livestock with little thought given to how these forages might affect the horse. That coupled with high-energy grains and supplements that many horse owners think are necessary has resulted in over nutrition of our horses.

The first step in getting your horse to a healthy weight is to admit that it is overweight. The key to managing your horse’s weight is balancing diet and exercise, and the first step is to determine their weight.

If a scale is not available, weight tapes work well or you can use a simple formula to calculate horses’ weight: Measure the horse’s heart girth and body length in inches, then plug in the following formula: (heart girth x heart girth) x body length/330= the weight of the horse in pounds

Once we accurately know a horse’s weight, we can calculate the pounds of feed he should receive. Horses placed on a weight-reduction plan should undergo a moderate level of exercise, producing an average heart rate of 90 beats per minute throughout the entire exercised period.

Ideally, they should be removed from pasture and placed on a hay diet that is by weight 1.5 percent of their body weight. A slow-feed hay net can help make limited hay last longer, to help satisfy the horse’s urge to eat. The hay should be fresh and contain less than 10 percent nonstructured carbohydrates. Nonstructured carbohydrates are sugars and glucose that are rapidly absorbed by the horse’s body. In fat horses or insulin resistant horses, high levels of blood sugar can contribute to laminitis development, which is the case in horses that grass founder.

Your local extension agent can test your hay to determine its carbohydrate level. If the hay is higher than 10 percent, you can soak it in a hay net in cold water for several hours to remove much of the sugar. Let the hay drain for 30 minutes before providing it to your horse. It goes without saying the water used to soak the hay should be discarded and not given to the horse.

If you cannot remove your horse from pasture, applying a grazing muzzle works great. The advantage of a grazing muzzle is that the horse exercises throughout the day but is able to eat a very small amount of grass.

Once your horse has reached its ideal body condition, maintaining the proper weight is a balancing act, and exercise will continue to be a key component. Because obesity can affect your horse’s health, schedule regular check-ups with your veterinarian; especially prior to and during the weight-reduction process.