Summary: by Beth Stelzleni of Mars Horsecare US, Inc. Horses that are in training or showing have vastly different nutritional needs than horses that are inactive. But itrsquo;s the level of activity is what determines how to feed our performance horses. The NRC categorizes the different activity levels into four categories: light, moderate, heavy, and very heavy. Horses in light activity are those used for events such as trail and pleasure, where the work is mainly done at the walk level ndash; and generally working 1-3 hours per week. Those in moderate work include school horses in a lesson program and those used for frequent showing -- but in disciplines that are less strenuous, and these horses usually work for 3-5 hours per week. When we get into the heavy work category, we start to see horses that work for 4-5 hours per week but undergo strenuous speed or jumping work during their training -- polo horses and those in low to medium level event training for example. Horses in very heavy work spend the bulk of their training doing strenuous activities including speed and jumping work and may work anywhere from 6-12 hours per week. These include elite racehorses and elite event horses. The higher the intensity of the work, the greater the energy requirement will be. Energy is the first nutrient that is required in higher amounts in the working horse, but the source of that energy is just as important as the amount. The first source of energy we see in equine nutrition products is soluble carbohydrates, or sugars and starch -- found mainly in grains, like corn, and sweetening agents like molasses. When a horse digests soluble carbohydrates, they are absorbed in the small intestine. The problem with soluble carbohydrates is that when they are digested they cause an increase in blood glucose and insulin that can lead to metabolic disturbances and increase the risk for tying up and ulcers, so itrsquo;s critical that we donrsquo;t overload the small intestine with them. If this happens, the starch that doesnrsquo;t get digested in the small intestine goes to the hindgut where it is fermented, which can cause acidosis, diarrhea, and even laminitis. If starches and sugars can be dangerous when fed in high amounts, what can we substitute as a safer energy source? And the answer is Fats - and these are actually the preferred energy source of the horse. As we train our horses and they increase in physical fitness, their bodies actually shift naturally from using carbohydrates for energy to using fats. Fats are also more energy-dense, meaning that a small amount of fat can actually hold a much larger amount of energy. Like sugar and starch, fats are absorbed in the small intestine but they do not cause a large metabolic disturbance, so they are safer than sugars and starches. Some sources of fats common in horse diets are vegetable oils (such as corn or soybean oil), flaxseed and rice bran. Fats also provide some additional benefits to performance horses. They improve the skin and haircoat, which is important in the show ring, for example. Fats can also calm behavior and make a horse more manageable. They reduce the heat load and delay lactate build up, both of which help to delay fatigue so the horse can go for longer periods. And since fats are power packed, we can feed less -- and the horse has a lower intake so carries around less gut fill. By lessening the gut fill, we can reduce the amount of weight the horse carries and therefore help him to jump higher or run faster. In addition to energy, water is a nutrient that is greatly affected as the horse starts to work. Performing horses lose massive amounts of water as they sweat, and this water needs to be replenished to keep the horse healthy. In moderate climates, horses can lose 6-8 L of sweat per hour, and this loss can increase to 15 L per hour in hot and humid climates. One L of sweat weighs about 2 pounds, so in a hot climate a horse can lose...
