Chewing the Fat

Obesity is a common horse-health problem.

It has been an accepted truth for decades: American people are overweight. And while we were sitting around eating potato chips, the phenomenon spread to our horses.

One of the main reasons behind equine obesity is that fat horses have become the aesthetic norm, argues Dr. Nat T. Messer IV, a professor of equine medicine and surgery at the University of Missouri’s College of Veterinary Medicine in Columbia.

“There is a generation or two of people who now think that a horse that is basically obese in the condition they keep him in for showing is what he should look like,” Dr. Messer says.

Referencing Orren Mixer’s famous rendering of the ideal American Quarter Horse, Dr. Messer observes that the animal featured in the painting has little to do with current accepted standards.

“That horse is not obese, and that horse does not look like many of the horses that are being shown today.”

And it’s extremely dangerous to the modern Quarter Horse’s health.

Weighty Problems

The most obvious cause of obesity in horses is the same one that applies to humans: They eat too much, and they don’t exercise enough. More specifically, they are fed too many nonsoluble carbohydrates that transform into sugar and, thus, fat.

“The most important cause is improper feeding, and feeding too much in the way of carbohydrates versus what horses are normally supposed to be eating, which is forage,” Dr. Messer explains. “Their system and GI tract was developed to exist on forage, and what we’ve done in the past several years is started feeding them diets that are high in energy and high in rich carbohydrates, and that has led to a significant increase in the number of horses that are obese.”

Overfeeding and under-exercising are management-related, but there are other conditions that play a role in obesity. This is where we start to hear the terms “equine metabolic syndrome,” “insulin resistance” and “equine Cushing’s disease.” The latter, according to Dr. Douglas O. Thal of Santa Fe, New Mexico, is a term that has fallen out of favor during the last five years.

“The veterinary term for Cushing’s today is PPID – pituitary pars intermedia dysfunction,” Dr. Thal explains, denoting an overgrowth of part of the pituitary gland. “It is extremely common in older horses – a horse that lives to 28 years of age and doesn’t have some degree of enlargement of that part of the pituitary gland is an unusual horse.”

Equine metabolic syndrome – also referred to as peripheral Cushing’s or insulin resistance – applies to horses who have problems in their hormonal makeup and with the way insulin works on the tissues of their bodies.

Dr. Thal describes it in this fashion: “If you think of that group of horses as the same as people that you know who eat a very small meal every day, but who are overweight, it’s the same situation,” he said. Metabolically, these horses tend to lay down fat in certain places – most commonly the crest of the neck, the topline and either side of the tail head. He adds, “In the old days, we called them ‘easy keepers.’ ”

While researchers are currently investigating how much of a role breed plays in equine obesity, its effect on Quarter Horses remains – for now – anecdotal. In Dr. Thal’s experience, hotbloods are less prone to becoming fat, gaited breeds demonstrate higher instances of obesity and Quarter Horses fall somewhere in between.

“There are definitely genetic groups of Quarter Horses that tend toward it, and there are genetic groups that don’t tend toward it,” he says. “The hotter, race-bred horses tend away from it, and the old-fashioned Quarter Horses that are heavy-boned, with calm demeanors, tend to be associated with it.”

Of course, once a horse is obese, the troubles don’t stop there: The fatter a horse is, the more predisposed it is to developing other conditions. One of the most obvious is increased wear and tear on the horse’s joints as a result of the additional weight.

One of the most serious is the dreaded L-word.

“Laminitis’ relationship to obesity is the critical issue,” Dr. Thal says. “That is the one thing that an obese horse gets that kills them, ultimately, if it’s not managed correctly, and if the diagnosis is not made of what is causing the laminitis.”

Without diagnosing – and treating – the causes behind the laminitis, you have little hope for effectively treating the laminitis itself.

Managing Weight

To maintain a healthy weight, Dr. Messer thinks most horses require little – if any – concentrated feeds, especially if they are not exercised on a regular basis.

“The average horse that is kept either in a barn or in a small pasture, and then is ridden two or three times a week can easily get along on what’s considered a maintenance ration, which doesn’t need to include carbohydrates,” he says.

If a horse’s exercise regime increases, additional carbohydrates can be incorporated into his diet … perhaps.

“There are people who don’t feed their horses many carbohydrates at all, who exercise their horses at a high level and get along,” he says. “It’s become dogma within the horse industry that if you’re going to work a horse hard, they are going to need this extra feed. In my opinion, that’s a bit of a myth.”

“We feed too much grain,” says Dr. Bruce McDavitt of McDavitt Veterinary Clinic in Zionsville, Indiana. “Unless you have a horse that is doing heavy work, it needs very little grain, if any at all.”

He recognizes that in environments where horses are on pasture, some stable managers feed grain as a means of coming into contact with their horses so that they can look them over once or twice a day.

If this is the case, Dr. McDavitt suggests feeding a small handful of grain and no more: “The majority of these horses are fine on hay, water and perhaps a mineral block if they are not getting much grain.”

The bottom line? Observe your animals and get your hands on them to judge their weight. In the wintertime especially, you may not notice how much – or how little – they weigh if their hair is long.

Dr. McDavitt also notes that it doesn’t hurt to buy a weight tape: “The accuracy may be questionable on some of them, but they do help you determine if the horse is gaining or losing weight.

On the Menu

So what, in a perfect world, should we be feeding our horses?

“We have to go back to what the horse was meant to eat,” Dr. Messer says. Sometimes, he admits, this can be expensive – the cost of hay is high, and traditional bagged feeds that are high in carbohydrates tend to be cheaper. While most manufacturers now produce feeds designed to address the obese horse specifically, he argues that they aren’t any less expensive than good-quality hay.

Regardless, Dr. Messer offers these guidelines: “Obese horses should have less than 10 percent of their diet in the form of soluble carbohydrates, which translates into sugar. Fiber and structural carbohydrates are what you find in most hay.”

It’s the soluble carbohydrates – those that transform into sugar – that are found in high levels in any feed featuring molasses, corn and barley, and which contribute to a horse becoming fat.

As mentioned, exercise is also a principle factor in getting your horse back into healthy form. For Dr. Thal, the utopia for a horse is being out on pasture and moving all day.

“That is the way they are designed, and anything that we do that deviates them from that path causes them a variety of problems – whether it’s colic, laminitis or obesity,” he says.

At the same time, he acknowledges that the reality, for many, is much different. In settings where pasture is limited, he advises maximum turnout in combination with regular exercise, such as trotting for at least 20 minutes several times a week.

“More is better, but multiple times a week instead of just once a week makes a big difference,” he says. “If you have a dry corral, get those horses out together so they can play among themselves. The more turnout and the motion any horse gets on a consistent basis, the better off they are.”

But what happens if you are trying to get your horse to lose weight and it is afflicted with laminitis? Lame horses, after all, can’t really move around that much. This is where thyroid hormone treatment is often applied: While years ago, there was some confusion as to the thyroid’s role in equine obesity, thyroid hormone supplementation is still used as a treatment against obesity.

“There is nothing wrong with their thyroid gland – fat horses do not have thyroid gland problems,” Dr. Messer says. “However, thyroid hormone supplementation will increase their metabolic rates, which helps them lose weight.”

This treatment is used not because the horse lacks thyroid hormone, but because the thyroid hormone’s contribution to weight loss enables horses to become less insulin resistant.

“If they are insulin-resistant and if they have laminitis, and if you correct the insulin resistance, it will also help them in healing from the effects of laminitis,” he explains.

As is the case with humans, when it comes to obesity in horses, prevention remains the best medicine. For Dr. Messer, this requires a shift in philosophy.

“Now, most people consider that ‘pretty’ equals fat, and that’s not the way we should think about it,” he says. “We should think about it as ugly being equivalent to fat, and go back to the more lean-bodied appearance that was the standard of excellence when Orren Mixer painted his model Quarter Horse.

“We have transitioned into this idea that horses need to be too heavy to look pretty. They may look pretty to those who have been brainwashed to think that, but they really shouldn’t be seen that way.”