Round-the-clock foraging is the most natural way for horses to eat, but “easy-keepers,” left to satisfy their own appetites, may consume more calories than they need. Photo by Betsy Lynch.

Horses become overweight for the same reason we do—they eat more calories than they burn. It isn’t any healthier for them than it is for us. Putting your horse on a diet could not only make your horse more active, but save his life. Overweight horses may lead to conditions of lameness, heart and lung problems, lethargy, and a slew of metabolic problems.

Lameness: Lameness is one of the most common health problems in horses. It causes pain for the horse and robs you of time in the saddle. The stress placed on your horse’s joints, tendons, ligaments and hooves is directly proportional to the horse’s weight. One of the most basic equations in physics (don’t panic, it really is basic!) is F = m x a, where "F" is force, "m" is mass (weight), and "a" is acceleration. The force your horse’s support systems experience with every step, at every speed, is influenced by his weight. An overweight horse traveling at the same speed as a leaner companion is subjecting his joints, tendons, ligaments and feet to greater stress. Sooner or later, it takes its toll. More strain is also put on the horse’s back.

Heart and Lungs: Horses aren’t prone to the same problems with fat-clogged arteries and heart attacks as people. But it’s still more work on their heart and lungs to move around an overweight body. If you take two relatively unfit horses, one lean and the other overweight, it’s not difficult to predict which one will be huffing and puffing sooner, even on a relatively easy trail ride.

Other Exercise Issues: A heavy layer of fat makes it difficult for your horse to regulate his body temperature during exercise. Working muscles generate a considerable amount of heat that the horse needs to lose through sweating, etc., to be able to continue exercising. In warm/hot weather, most people’s peak riding seasons, the overweight horse is at greater risk of dangerous overheating and heat stroke.

Metabolic: Fat tissue isn’t just an inert, jelly-like mass. Fat cells actively secrete a variety of substances with hormonal effects. Overweight horses can be more likely to be insulin resistant, a pre-diabetic state that results in even more weight gain, abnormally increased appetite, and increased risk of laminitis.

Lethargy: It’s always nice to work with a cooperative horse, but we don’t want that to be because the horse doesn’t feel well. The more overweight a horse becomes, the less active he is and the less interest he finds in his surroundings (except food). Horses are extremely athletic creatures by nature, not normally dull, apathetic and listless. Becoming overweight can rob your horse of that interest in life and movement.

One thing that holds people back from trying to get their horses to a better weight is fear that the horse will have to be "starved" to get there. This simply isn’t the case. Your horse can have plenty to eat and still lose weight. The trick isn’t how much you feed him—it’s what you feed.

Weighty Issues • Formal exercise is essential to keeping excess weight off a horse. • Feed horses 2% of their body weight in hay per day, less if you’re feeding grain or other feed supplements. • Horses like hay, so you are not depriving your horse by cutting back the grain. • Substitute fresh green vegetables, sugar-free peppermints, or maybe apple peel as treats. • Horses who tend to get heavy on pasture may need a grazing muzzle.

What to Feed
Horses evolved to eat grass—but also to have to travel large distances every day to find enough of it. They did not evolve eating grains of any type, and certainly not fat. They did not evolve confined to relatively small areas, turned out on fields seeded with strains of grass designed to stand up well to heavy grazing. We can’t duplicate the living conditions of a free-living horse, but we can make sure we feed him sensibly.

Later in this article are some programs for mildly and severely overweight horses. But first consider a few general principles.

First of all, the horse can only eat what we choose to feed him. He can’t cheat—but owners can, and this is what usually compromises efforts at weight loss. Sure your horse would enjoy having grain put in front of him several times a day, just like many of us wouldn’t mind topping off each meal with a slice of chocolate cake. But that doesn’t mean it’s good for him.

Don’t make the mistake of thinking your horse is having cravings, feeling deprived, or blaming you for taking away his goodies. Horses like hay.

Once in a while, a horse that has been spoiled by being fed too much calorie-dense, highly palatable feed will pout and refuse to eat that perfectly good hay. Don’t worry—he won’t starve himself. Even if you think the horse is barely eating, just wait it out. He’ll come around in a few days’ time, and soon it will be that hay he’s yelling for when he sees you—and cleaning up every last bit.

Once you get your horse on a healthy weight-loss program, don’t disrupt it by feeding him high sugar/starch "cookies," donuts, candy or any human food. Instead, substitute small amounts of fresh green vegetables (experiment to see what he likes), sugar-free peppermints, or a few mint-flavored antacids, apple peel (no sweet fruits please), alfalfa pellets, or cubes. This switch may be a bit of culture shock for both of you to start, but your horse will adapt quickly to the new offerings, probably quicker than you do.

Get Your Horse Moving
Exercise, exercise, exercise is also an important part of the picture. Turning the horse out is better than stall confinement, but it’s not the same thing as formal exercise. Formal exercise means the horse keeps moving for an extended period of time, a bare minimum of 20 minutes, without breaks to enjoy the scenery or snatch some grass.

Regular exercise does more than just burn some calories. It changes the way the body handles them. For up to 24 hours after exercise, calories are preferentially diverted to the horse’s muscles to replace energy stores there, repair any minor damage, and build muscle bulk.

On days you can’t ride, lunge your horse or work him in the round pen. If you can’t be there at all, try to arrange for a friend to pony your horse while they are riding theirs, or find someone willing to work your horse for you.

Weight loss goes much easier when calories are being used for more than building up fat. The more the horse works, the more he’ll be able to eat without packing his food on as extra fat.

As you look at what to feed the overweight horse, be aware that many feeds on the market today are advertising high fiber or low carb/grains. That’s a good start, but most of them have added fat to replace the grain portion, and none are labeled with the calorie content. So you really have no way to compare them.

Body Image So many horses are living relatively inactive lives, and are overweight as a result, that many people really don’t know what a normal weight looks like. Your horse doesn’t have to be as lean as a racehorse, but he shouldn’t be fat either. The Heineke body condition scoring system is a useful tool for evaluating how much fat is on the horse. Usually, the ideal horse will be a 5 or 6, depending on his body type, age and level of activity. If you have been told things like your horse’s breed is "always round" or "always has a cresty, thick neck," don’t believe it. It’s also not true that ponies are "supposed to be fat." Take a look through breed books or enter your horse’s breed into an Internet search to get a good idea of what they are supposed to look like. Many people have trouble distinguishing a fatty crest, which no horse should have, from a muscular neck. When your horse is standing with his head up, in an alert but not exaggeratedly elevated position, the topline of the neck should run in a smooth, straight line from the top of the head to the withers. Also, if you are looking down your horse’s back and seeing a deep groove, don’t be too quick to congratulate yourself on having good topline and back-muscle development. This is one of the first areas to accumulate fat. A well-muscled back is flat, with muscle even with the level of the tips of the spine. Anything on top of this is fat.

To complicate matters further, horse feeds aren’t required to list their ingredients with the main ingredient first and other ingredients in descending order like human food labels do. A feed may list alfalfa or "forage products" first and corn last, but still have just as much corn in it as hay, or even more.

You can find some clues, though. First, check the fat content. A horse that needs to lose weight should never be eating something higher than 3% to 4% fat. Also, unless the feed specifically states it is low calorie, avoid feeds with molasses in the ingredients list. Some have very small amounts, while others have quite a lot. It’s not necessarily easy to tell how much is in there, especially with a pelleted feed.

Crude fiber doesn’t necessarily correlate directly with calories because high-soluble fiber ingredients, like beet pulp, are actually more calorie dense than hays. But it is a fairly good indication of how much grain/grain products are in a feed. Look for one with at least 20% fiber, like Triple Crown Lite Formula or Agways Superior Extra Lite. Some complete feeds fit the bill too, and make good substitutes for straight grains.

In addition to the fat and fiber content, check the feeding directions. If the feed calls for giving the horse about 1.5% of his body weight/day when used as a complete feed (i.e., 15 lbs./day for a 1,000-pound horse not in work), it has a calorie content similar to a high-quality hay. Nutrena’s Complete, for example, has 20% fiber, 2% fat.

Mildly Overweight
A mildly overweight horse has a body condition score between 6 and 7. It’s okay for a mare about to foal, because she will have tremendous demands for calories when she starts to produce milk, or for a horse heading into winter in an area with very extreme cold. Otherwise, this is too much extra weight for a horse to be carrying around.

These mildly overweight, "fleshy" horses may only need more regular exercise. There’s certainly no harm in trying that first. If exercise alone doesn’t make a difference, you need to revise the diet.

To begin, ask your vet to estimate what your horse’s normal, healthy weight should be. Next, figure out how much grain and hay you are feeding. You want to be giving the horse about 2% of his ideal body weight in hay per day.

If you feed more than hay, use the chart at the end of this article to figure how much you are feeding in hay equivalents.

For example, most horses weighing about 1,000 pounds will hold a normal weight eating 20 to 25 pounds of hay per day. If you are feeding your mildly overweight horse 20 pounds of hay plus 5 pounds of a commercial grain mix, you’re giving him the equivalent of 32.5 to 35 pounds of hay because of the higher calorie level in the grain. This is enough to maintain a body weight of as much as 1,625 pounds if your horse is a fairly easy keeper.

If you have calculated that you are feeding your horse more than the equivalent of 2% of his body weight in hay, cut back to what 2% of his ideal body weight would be. Cut out concentrated calorie sources first—i.e., grain and fat.

The more different types of hay you feed him, the better chance his mineral intake will be fairly well balanced. You can then give him a balanced pelleted supplement instead of grain at mealtime. These are usually fed at a rate of about 1 pound per day. Some examples of pelleted protein/mineral supplements are the Doctor’s Choice Equi-Shine line, www.equishine.com, Triple Crown 12 or 30, www.triplecrownfeed.com, and Buckeye Gro N’ Win.

If it makes you feel better to give the horse a more substantial amount in his feed tub, choose from the "lean cuisine" menu at the end of this article. Also given are the hay equivalents, so you know how much to subtract from the amount of hay you are feeding.

Severely Overweight
A severely overweight horse has a body condition score of 8 or higher and is definitely fat. The same general principles apply as with the moderately overweight horse, but your target feeding level, as hay, is either 2% of the ideal body weight or 1.5% of the current body weight, whichever is higher. Paradoxically, if you cut back too much on calories, the horse may actually have more trouble losing weight.

Exercise is extremely important to the severely overweight horse. However, you should limit it to walking and light trotting until the horse loses some weight to avoid overstressing his feet and joints.

If your overweight horse has pasture instead of hay, your choices are to dry lot him and feed a known quantity of hay or invest in a grazing muzzle.

The Best Friend Muzzle, www.bestfriend equine.com, is sturdy, stays in place well, has breakaway features in case of accidental snagging, and restricts grazing but not drinking. It also has a plug for the end to prevent grazing completely. This feature can be used for horses that still don’t lose weight with restricted grazing (plug completely for part of the day), or to keep horses that have only limited grazing from getting access to grass when they are turned out.

Never underestimate the amount of grass a horse can pack away in even as short a time as an hour. In fact, in some cases of moderately overweight horses, preventing grass intake may be all you need to do to get the desired weight loss.

As with everything about feeding horses, the above are only general guidelines. Some horses may need their daily feed reduced a bit more to lose weight, especially if the horse is not being exercised. Monitor your horse’s progress with body-condition scoring every two to four weeks, as well as weight-tape measurements.

Weight losses of between 40 and 75 pounds per month can be expected with the program here. Don’t be in any rush to get the weight off. Your horse didn’t put it on overnight, and he won’t lose it overnight either. Better to go for steady weight loss with the horse getting enough to eat to feel satisfied.