How can you keep your metabolically efficient horse healthy when he’s laid up with injury or chronic illness?

Owning an easy keeper can be a blessing and a curse. On the one hand, there’s the bliss of lower feed bills. On the other, the looming threat of laminitis. It’s particularly challenging when one of these “air ferns” becomes injured or lame and can’t work off his weight. Dropping from high levels of exercise to little or no exercise can wreak havoc on metabolism.

The last thing you want, on top of the lameness, is for your injured horse to pack on the pounds. Weight exacerbates not only metabolic issues but also musculoskeletal ones. So here are some pointers for rehabbing horses while also watching their weight.

What Are the Risks?

There are plenty of reasons to be concerned about your horse putting on weight, especially when he’s recovering from an injury or dealing with a chronic lameness. “Additional weight means more stress on injured areas, even if the horse is only standing still,” says Eleanor M. Kellon, VMD, owner of Equine Nutritional Solutions, in Robesonia, Pennsylvania. “Excess weight also impedes temperature regulation in the heat and makes the heart work harder. Even breathing can be more difficult. The extra weight makes it tougher for the horse during reconditioning and increases the risk of re-injury.” 

The greatest risk, though, is that of developing the hoof disease laminitis, she says. That’s especially true for horses prone to insulin resistance (IR), which is a reduced sensitivity to insulin that makes it harder for fat, muscle, and liver cells to transport glucose out of the bloodstream and store it as the fuel source glycogen. 

“Horses that become obese can develop a degree of IR that can be detected by sensitive intravenous testing,” Kellon says. “Horses on forced inactivity are also going to be less insulin-sensitive than they are when working hard.”

Is Your Horse at Risk?

One of the serious health risks associated with weight gain is insulin dysregulation, the umbrella term under which IR, equine metabolic syndrome (EMS), and hyperinsulinemia (high insulin levels in the bloodstream) fall. The condition occurs more frequently in ponies and certain horse breeds, such as Morgans, Warmbloods, and Arabians, says Andrew van Eps BVSc, PhD, MACVSc, Dipl. ACVIM, associate professor of equine musculoskeletal research at the University of Pennsylvania’s School of Veterinary Medicine (Penn Vet), in Kennett Square.

These horses and ponies are at particular risk of developing complications from insulin dysregulation, namely laminitis. If they can’t exercise because of their primary lameness problem, they need to be monitored closely for weight gain during their time off, van Eps says.

The highest risk category is the horse that’s genetically prone to IR but has been in hard work until the time of injury, says Kellon. “The endurance Arabian is the classic example,” she says. “Such a horse can gain weight rapidly, show obvious insulin resistance changes on blood work, and even become laminitic within a few weeks if diet is not properly controlled.”

If you’re in doubt about whether your horse has insulin dysregulation, you can request an oral sugar test from your veterinarian, says van Eps.

If you’re fortunate enough to have a horse that appears unlikely to develop insulin resistance, you’re not completely off the hook. Our sources point out that even “normal” horses are subject to insulin upset if they go from hard work to no work without corresponding diet changes.

Getting the Rations Right

Your greatest weapon against an obese rested horse is diet. The horse’s ­reduced activity level leaves you little choice but to keep an eye on what and how much he’s eating. But it’s not just a question of reducing quantities; it’s about ensuring your horse is still getting plenty of nutrition, just with fewer sugars and starches.

“For all active horses suddenly put on rest, it’s important to adjust the calories to prevent weight gain while preserving adequate protein and vitamin/mineral intake,” Kellon says. “Fortunately, this is easily done by moving to a forage-based diet. There’s no reason to wean off grain slowly. Just stop it.”

The exact calorie drop will depend on the situation, Kellon says. “The horse on paddock rest will expend more calories ambling around than while just standing, but can still easily gain weight if fed the same as when being actively worked,” she says. “A show hunter or dressage horse will need about a 22% drop in calories, while an endurance or upper level event horse needs about 32% less, even if they are moving around in the paddock.”

Meanwhile, the IR-prone horse will need even more attention to his calorie intake. “That horse will be on the lower end of the range for calorie requirements because he’ll gain weight more easily and will also require a combined sugar (ethanol-soluble carbohydrates, or ESC) and starch intake of no higher than 10% (of the diet),” says Kellon.

Be careful not to confuse lower-ESC/starch hay with poor-quality hay, however. You’ll want the quality to be high for good nutrition. “Even resting horses need nutrients,” says Daisy Bicking, a Pennsylvania-based farrier who rehabilitates horses with metabolic disorders and laminitis. “To maintain a healthy weight without getting fat, they just need hay that isn’t too high in ethanol-soluble carbohydrates and starches.”

You can get your hay tested to know what its composition is. But if you can’t test it or get access to low-ESC/starch hay, you can soak it in water for 45 minutes to remove most of the sugars, van Eps says. Just be sure to toss the water immediately so the horse doesn’t consume it, too.

With low-ESC/starch hay, you should be able to feed a normal amount of forage—about 2% of body weight (so, about 20 pounds a day for a 1,000-pound horse), Kellon says, to maintain weight. A horse that needs to lose weight should eat about 1.5% of his body weight in hay per day, van Eps says.

Distribute the hay with a slow feeder or a net, says Bicking. This keeps the horse busy and helps regulate his insulin levels.

Also monitor how well your slow feeder works. “If there’s no hay by morning, you should slow the horse down more,” says Bicking. A different kind of slow feeder or doubling the haynet can help slow intake.

Dietary Extras

While hay is the primary food source for these restricted-exercise horses, they still need a balanced diet of protein, vitamins, and minerals. These are especially important for the healing process in injured horses, says Bicking.

But knowing whether your horse is getting enough nutrients is difficult because you can’t always judge it by body condition like you can with calories. Again, hay analysis can help. It is “by far the best way to determine how much the horse is taking in from his diet and what the supplement needs are,” Bicking says. “A good-quality grass hay will almost always meet, if not exceed, total protein needs, but adding 7 to 10 grams of supplemental lysine may be wise because it’s an essential amino acid for protein assembly, including the collagen of tendons and ligaments. Horses on hay rather than pasture need at least 1 IU/lb of vitamin E supplemented and minerals, depending on the hay analysis.”

If your hay is at least a year old, you might need to supplement with vitamin A at 20,000 to 40,000 IU per day, she adds. Vitamin and mineral supplements could be useful if you change your hay regularly (and don’t get it tested), just to be sure your horse is consistently getting the nutrients he needs during his layup.

Be careful about giving your rested horse sweet treats. While you might be tempted to load him with apples, carrots, and packaged horse treats as an expression of love and compassion, these offerings could do more harm than good. 

If you really want to feed your patient something, try a low-sugar treat, such as a peanut butter-based product, van Eps says. While high in fats, the sugar and starch levels are low enough to keep the horse’s insulin levels down.

Horses might also enjoy low-calorie treats such as hay pellets and cubes, dried split peas (a great protein source), and beet-pulp-based treats, says Kellon.

And if you don’t want to ignore your horse completely at mealtime, offer him a bucket of hay pellets with any needed supplements rather than grain.

Exercise Options

If your veterinarian prescribes strict stall rest, there’s not much getting around that. You can hand-walk your horse, with your vet’s permission, but hand-walking—while giving the horse a good mental break from the stall—still doesn’t provide much useful exercise unless the horse is walked a lot, says van Eps. Check with your veterinarian to see how many hours your horse can be on an automatic walker. And if you don’t have a walker, prepare to get as much exercise as your horse on those hand-walking outings.

If your horse can have paddock time, this can be good exercise. But if he tends to just stand around, you might need to encourage him to move by putting food and water in different areas, says van Eps.

Swimming might be an option for some horses if you have access to an equine pool or horse-safe pond; if the veterinarian authorizes the movement to and from the water source; and if the horse reacts well to swimming, says van Eps. You could even try “fancy therapy equipment” such as an aqua treadmill if it’s available, he adds.

If the horse’s lameness is hoof-related, water activity might be contraindicated, says Bicking. “Walking in water would make the feet soft,” she says. “And most aquatic therapy centers don’t want shoes on horses for swimming or treadmill work. So if the horse needs shoes therapeutically, swimming or water work might not work.”

Core exercises might sound tempting to try during stall rest, but they probably do little good in the way of calorie expenditure, our sources say.

Take-Home Message

Managing lameness is complicated in domestic horses because it means having to rest an animal that thrives on movement. To keep your unsound horse healthy, adjust his food intake according to his new needs and keep a close (ideally, weekly) watch on his weight, girth circumference, and body condition score. Spread out his meals as much as possible to keep him occupied and his digestive system moving. And keep in touch with your veterinarian about his progress, especially with regard to permitted exercise levels as he heals. With good care and a watchful eye, your lame horse should be able to progress back to healthy soundness without the additional burdensome complications of metabolic disorders.