the DE, the less your horse will need to eat to keep him fit—not fat. The most practical way to evaluate your horse’s digestible-energy requirement is simply to watch his weight. Is he fat? He needs less. Is he thin? Feed him more. Exercising horses, pregnant and lactating mares, and growing youngsters will have higher energy needs than sedentary horses.
Protein: Protein requirements also vary among different types of horses. A sedentary horse or a horse in light work requires 10 to 11 percent protein daily, while a high-performance horse, broodmare, or growing youngster needs closer to 12 to 14 percent. How can you tell if your horse is protein-deprived? Visual clues include a noticeable lack of muscling along his back and topline along with a potbellied look.
But how much is too much? Contrary to popular belief, too much protein really won’t cause a problem for your horse. A high-protein diet may result in greater urine production and higher ammonia levels in the urine, but that’s more of a stall-cleaning nuisance than a health risk. And most higher-protein feeds also have higher digestible energy, meaning they provide a lot of calories.
Carbohydrates: Finally, carbohydrate content has gained quite a bit of attention in recent years, primarily because we’ve learned to recognize horses with health issues—such as insulin resistance and polysaccharide storage myopathy (PSSM)—can experience severe consequences when fed high-carbohydrate diets. Hay’s carbohydrate content can be expressed in three ways: (1) non-structural carbohydrates; (2) water-soluable carbohydrates; and (3) ethanol-soluable carbohydrates.
The term “non-structural carbohydrates” (NSC) refers to starch and sugars broken down in the small intes- tine and absorbed as glucose into the bloodstream, which is risky for a horse with a sugar-sensitive condition.
Nutrition “purists” prefer to look at water-soluable carbohydrates (WSC), which include simple sugars without starch, as well as ethanol-soluable carbohydrates (ESC), which help to separate out a specific type of sugar molecule called fructan (risky for a laminitis horse).
For practical purposes, if your horse is sugar-sensitive, your vet will recommend looking for an NSC value that’s less than 10 percent, although in many cases this is difficult to find. A WSC less than 10 percent is often a more reasonable goal.