When you're feeling under the weather, sometimes all you want is a nice, hot bowl of chicken soup. Other times, you might hunger for a full-course meal of roast beef, mashed potatoes, and steaming green beans. Even a mild injury that keeps you planted on the couch instead of sweating at the gym might change the way you think about food, urging you to cut back those desserts to hold your waistline in check. Likewise, your horse's dietary demands can change when he's ill or injured.

The good news is that if your adult horse is already eating a normal, balanced ration, you often won't need to alter that diet plan if he gets sick, says Sarah Ralston, VMD, PhD, Dipl. ACVN, associate professor of animal science at Rutgers University. While a sick horse's metabolic rate does typically increase, his activity level usually decreases, she explains. So the portion of feed that might normally go toward a schooling session is now redirected to aid the body's recovery efforts. In fact, since horses have such sensitive digestive systems, it's best to avoid making any drastic changes to an ill animal's diet, says Ralston.

That said, there are some situations where a change in ration can enhance progress toward good health or improve the horse's quality of life. For instance, stress–like that caused by surgery, orthopedic problems, or illness–increases the horse's B vitamin and vitamin C requirements. So, says Ralston, supplementing these vitamins might benefit an ill or injured horse.

If your horse is stall-bound from a lameness or orthopedic issue, he'll benefit from reduced grain intake and free-choice hay, notes Ralston. The lowered carbohydrates (grain) will keep his energy levels suited to confinement, and the increased roughage (hay) will not only keep his digestive system humming along, but will also help ward off the boredom of inactivity