Working Hard or Hardly Working? Equine Work IntensityBy Kentucky Equine Research Staff · September 23, 2009
Optimal nutrition of the performance horse hinges foremost on the exercise it performs. Just as the diet of a human bodybuilder is dissimilar to that of a marathon runner, most horses are fed with performance goals in mind. Therefore, accurately assessing the level of work performed by a horse is essential in determining the amount and type of feed offered.
Energy is produced by aerobic or anaerobic metabolism. The breakdown of carbohydrates, fats, and protein into energy with the involvement of oxygen is termed an aerobic reaction. Because oxygen is required, this energy-producing process is slow. The conversion of glucose or glycogen to lactic acid does not require oxygen and is therefore an anaerobic reaction, a process that produces energy quickly. Equinenutritionists divide work into three classes based on how horses derive energy from their bodies to fuel exercise.
High-intensity, short-duration work includes performance events with a primary sprint component. Quick acceleration and top speed over a short distance require anaerobic energy production. Examples of high-intensity, short-duration work are thoroughbred, Standardbred, and Quarter Horse racing; barrel racing and pole bending; rodeo events such as heading, heeling, calf roping, and steer wrestling; and draft horse pulling contests.
Traditional carbohydrate-laden feeds, which include most low-fat textured or pelleted concentrates, and forage may satisfy the nutritional requirements of horses performing this type of exercise. The digestion of carbohydrates provides muscles with glycogen, a fuel critical for high-intensity performance. As workload increases and energy reserves empty, large quantities of complex carbohydrates may be offered to the horse in an attempt to maintain body condition. As carbohydrate intake rises, the risk of colic and laminitis escalates. Replacing a fraction of the carbohydrate content of the diet with energy-rich fat is one way to reduce the risk of metabolic disorders while supplying necessary calories.
Horses fed high-fat rations typically require fewer pounds of feed to satisfy caloric requirements because fat delivers 2.25 times the energy of an equal amount of carbohydrate. Fat is becoming an increasingly popular nutrient among those caring for horses with elevated energy requirements. Research has proven that feeds too rich in protein may negatively affect performance. From an economic perspective, diets overly abundant in protein should be shunned as protein packed feedstuffs are far more expensive than other energy sources.
Moderate-intensity, medium-duration work encompasses exercise that taxes but not necessarily exhausts a horse and requires aerobic and anaerobic energy production. The primary moderate-intensity, medium-duration work involves intensive show training and competition. Horses are asked to perform for several minutes, perhaps close to an hour, and often more than once per day.
Feeds formulated for horses performing moderate- intensity, medium-duration work should be similar to those fed horses involved in high intensity, short-duration performance. One primary difference, however, involves feeding management. Horses in this classification may require less feed to support the work effort.
Low-intensity, long-duration work includes endurance activities that typically last two or more hours. Aerobic energy production is required to sustain this type of exercise. Examples of low-intensity, long-duration exercise include endurance races, competitive trail rides, and draft horse, ranch horse, and heavily used school horse work.
As workouts become longer, high-quality forage, that which is low in indigestible lignin, becomes more imperative in the diet. Not only is fiber a source of energy, but it holds water and electrolytes in the hindgut. Horses can draw on these reserves during exercise, effectively suppressing dehydration. In particular, beet pulp and soybean hulls are considered “super fibers” because of their high bacterial fermentation rate and water-holding capacity.
Not all equine athletic endeavors fit neatly into one of these broad classifications. Some activities mesh properties of more than one. With its long twisting courses and explosive jumping efforts, show jumping, for instance, represents both high- and moderate-intensity activity. Polo, a fast-paced sport of sudden accelerations and abrupt stops mixed with easy canters and full-tilt gallops, combines all three exercise classes.
Simpler explanations of workloads, ones that may be easier for horse owners and feed manufacturers to relate to, appear below. These designations are often listed as part of the feeding instructions on feed bags or tags. Horses in light work are exercised three or four times weekly in preparation for trail riding, pleasure driving, or as light training for low-key show events such as western pleasure, trail, and lower-level dressage.
Horses in moderate work participate in a near daily, structured training program. Reining horses, jumpers, upper-level dressage horses, polo ponies, endurance horses, and young racehorses undergoing breaking and training would fall into this category. Horses involved in rodeo events are also included in this category.
Horses in heavy work train and compete at the peak of their physical abilities. Racehorses (thoroughbreds, Standardbreds, Quarter Horses, etc.) on an active racing schedule and three-day event horses preparing for competition fit into this classification. Few horses that participate in typical pleasure rides, horse shows, or rodeos fit in this grouping.
Deciding the intensity of a horse's exercise program is not difficult, but owners are often left to determine this on their own with few or no guidelines. Using these basic classifications, caretakers and consultants can accurately as certain the workload of a horse and can feed bit accordingly