Veterinary experts say it’s best to avoid any temptations to take an easy road to a cure when dealing with equine metabolic syndrome.
“Dietary restriction and exercise are certainly the preferred and ideal treatments for EMS, and the use of pharmaceutical agents to avoid these hard management changes is not recommended,” said Rose Nolen-Walston, DVM, assistant professor of Large-Animal Internal Medicine at Penn Vet’s New Bolton Center in Kennett Square, Pa.
Dr. Nolen-Walston stressed the importance of exercise in dealing with EMS.
“Exercise can be as simple as pasture turnout if grass consumption can be limited, especially in a herd of horses including some youngsters who keep the herd active,” Nolen-Walston said.
“Additionally, gradual increases of ridden, driven or longeing work should be added as appropriate for the horse if no laminitis signs are present. Swimming is ideal but not available to most owners, and so the goal of slow, steady exercise is usually the best way to go when trying to reduce weight and improve insulin sensitivity.”
Describing the disease and the number of ways it can affect patients is a starting point for Nicholas Frank, DVM, Ph.D., Dipl. ACVIM.
“EMS is a clinical syndrome with the components of increased adiposity, insulin dysregulation (hyperinsulinemia, insulin resistance) and hypertriglyceridemia,” said Dr. Frank, a professor and department chair in the Department of Clinical Sciences at the Cummings School of Veterinary Medicine at Tufts University.
“Horses and ponies with EMS have a higher risk of developing laminitis and also pedunculated lipomas, infertility and hyperlipemia.”
That’s a good explanation for veterinarians, but breaking it down for horse owners so they can understand the importance of treating EMS is crucial, said Steve Reed, DVM, Dipl. ACVIM.
“What I usually tell my clients is that your horse has a high body condition score and the phenotypic characteristics which have been shown to be associated with metabolic syndrome, meaning they have cresty necks and fat over the shoulders, tail head, topline and ribs,” said Dr. Reed, who practices at Rood and Riddle Equine Hospital in Lexington, Ky.
Reed explains to horse owners that to combat these issues and to prevent laminitis they need to decrease starches in the diet, to turn the horses out with a grazing muzzle and that they need to start increasing their exercise level slowly but on a daily basis.
While Nolen-Walston believes that diet and exercise are the best way to go, there are some drugs she believes can help.
Metformin, used to improve insulin sensitivity in humans, has some small benefits on horses, she said.
“It’s unlikely that it works in the same way in horses compared to humans, as very little of the drug is absorbed through the GI tract,” she said. “However, it may have a local effect on the intestines themselves that may provide benefits to horses that are not able to be adequately restricted from high-calorie diets.”
A second medication Nolen-Walston said is appropriate for only short-term use is the thyroid replacement levothyroxine.
“Although horses with EMS do not have thyroid disorders and the very diagnosis of hypothyroidism in horses is very scientifically questionable, this drug may improve insulin sensitivity and help horses lose weight in the first three to six months of treatment for EMS,” Nolen-Walston said.
Where levothyroxine is administered to accelerate weight loss in obese horses, metformin is administered when all of the usual strategies have been tried and hyperinsulinemia persists, Frank said, adding, “It’s given 30 to 60 minutes prior to feeding to blunt glucose responses.”
There are several things to consider when contemplating a weight loss and exercise program with horses.
Initial steps should include a complete veterinary examination to ensure the horse is in good health, and ensuring there is not a flare up of laminitis that would preclude a structured exercise plan, said New Bolton Center’s Nolen-Walston.
“First, horses with EMS should receive extremely limited access to grazing, especially when the pastures have the highest levels of sugars within the grass,” she said. “The danger periods for grazing are during the spring and autumn, when the days are warm but the nights are cool, especially late morning and through the afternoon.”
Ideally, Nolen-Walston said, horses with EMS should graze only before 10 a.m. or on cloudy days.
“Mature, unstressed grasses have the lowest levels of sugars, but a hungry horse will eat with great determination if given only a few hours a day,” she said.
Use of a grazing muzzle can allow horses to gain exercise at pasture while reducing intake, Nolen-Walston said, adding that some horses can still eat dangerous amounts of grass even with this device.
Hay should be tested for its nonstructural carbohydrate levels, and Nolen-Walston recommends hay with a non-structural carbohydrate level below 10 percent—although soaking higher NSC hay prior to feeding can somewhat reduce the levels.
Additionally, she advises that overweight horses and ponies receive only roughly 1.5 percent of their bodyweight in hay, which can be slightly reduced if weight loss is not being achieved.
“No grain or concentrate is needed for horses on good quality hay, although a vitamin and mineral supplement and possibly a protein supplement should be added to maintain a balanced intake of nutrients,” Nolen-Walston said.
In fact, some breeds and strains of horses need only 1 percent of their bodyweight to achieve weight loss.
“With enough dedication from owners, even the most rotund of ponies can achieve a healthy body condition,” she said.
How much weight reduction is necessary to improve a horse’s condition?
“To me this depends upon genetics, the chronicity of obesity, and other exacerbating factors such as PPID (for hyperinsulinemia),” said Frank with Tufts University. “It also depends on how you define condition – BCS, internal fat, subcutaneous fat thickness.”
Take, for example, a young quarter horse that has been allowed to become obese and has insulin responses that are abnormal yet mild, Frank said.
That horse will respond quickly to weight loss and return to normal insulin values. An obese hyperinsulinemic pony that has battled it for 20 years, on the other hand, is a “real battle,” Frank said.
When it comes to weight loss there is no perfect amount for horses with EMS, and not all are even overweight, said New Bolton Center’s Nolen-Walston.
“However, the majority of horses and ponies with EMS have too much body fat stores, and most have body condition scores of over 7/9,” she said. “All of these horses should be aimed at a BCS of 4-5/9, where the last rib can be seen and the other ribs felt easily without a layer of fat.”
How much weight loss should be achieved is a difficult question, agreed Reed.
The difficulty is because the BCS does not appear to be as accurate once a horse is greater than 1,200 pounds or has a BCS of 6 due to the amount of intraabdominal fat, he said.
“Therefore, you might consider that to change one level of body condition score you need to reduce the weight by 50 pounds, so if a horse has a BCS of 8 out of 9 and you want to bring it down to a 6 it needs to lose 100 pounds of body weight,” Reed said.
Several experts use the numerical Henneke horse body condition scoring system developed at Texas A&M University to determine the amount of fat on a horse’s body where 1 represents an emaciated horse and 9 is for an extremely fat horse. On this scale horses begin to be considered “moderately fleshy” at 6, moving to “fleshy” (a spongy tail head, fat deposits around the neck and shoulders) “fat” and “extremely fat” with a BCS of 9.
A Mississippi State University flier details how to evaluate BCS for horses:
Horses that are fed free-choice hay will often develop a “hay belly.” When foals are weaned, they will also develop a prominent belly. This is from gut distention and should not be confused with fat.
Pregnant mares in late gestation will develop an enlarged belly. It is important to know if the mare is pregnant so that you can meet her nutrient requirements.
Not all horses are proportioned equally. Horses that are tall and long will look leaner than short and compact horses.
Horses will grow longer hair in the winter and often appear fatter than they truly are.
The Kentucky Horse Council advises that to determine a horse’s overall body condition score, six key areas need to be examined: back, ribs, withers, neck, shoulder, tail head.
“There are a lot of supplements and nutraceuticals that are aimed at both humans and horses with insulin resistance and metabolic syndrome,” said Nolen-Walston. “Sadly, for most of them, there is either an absence of evidence, or data from good quality clinical trials where investigators and owners/patients are blinded to whether they are receiving a treatment or placebo drug do not support the use of the product.
“Although many of these products are benign, owners shouldn’t rely on them to prevent the harmful effects of EMS that are not controlled through diet and exercise.”
Reed noted: “Oxidant damage contributes to lipotoxicity and lipid-induced programmed cell death, which might explain the ‘why’ for use of antioxidant agents.”
Rood and Riddle uses products like vitamin E, and agents like EO•3 made by Kentucky Equine Research or Metaboral by Equithrive, which contains Resverasyn, a micro-encapsulated resveratrol.
“They are becoming more popular and are products that we use to deal with metabolic syndrome and horses with the clinical features like obesity and laminitis,” Reed said. “These products seem to have an impact on insulin sensitivity and at several research seminars and public veterinary meetings, the data appear quite promising.”
Body Condition Scores for Different Equine Disciplines
Open mare: 4-6
Stallion (off season): 5-7
Standardbred racehorse: 4-6
Thoroughbred racehorse: 4-6
Show Jumper: 5-7
Breeding stallion: 4-6
Quarter Horse: 5-7
Show hack: 5-7
Pregnant mare: 6-8