The onset of signs of fatigue is something we aim to avoid during physical activity or competition. Fatigue has a multidimensional nature, depending on the activity performed (intensity, duration, and type of activity), the horse’s physical conditioning, its physiological state, and the environmental conditions (temperature, humidity, altitude, and pollution) to which it is subjected.
Fatigue is often associated with factors such as the depletion of muscle glycogen stores, the accumulation of metabolic by-products and muscle acidification, electrolyte loss, hyperthermia, among others.
Nutrition plays an important role in exercise, providing the energy sources necessary for energy production. In general, energy sources are fats and carbohydrates, used in the form of fatty acids and glucose.
Predominantly aerobic activities (long duration, low intensity) mainly use energy from fatty acids, while anaerobic activities (short duration, high intensity) predominantly use glucose. During physical effort, horses use both forms of energy production, relying more on one or the other depending on the type of exertion involved.
Feeding management practices to help reduce fatigue in competition horses:
Ensure proper hydration
We must ensure that the horse drinks water. Good hydration is essential for the organism’s homeostasis, as well as for proper thermoregulation, which is fundamental in preventing fatigue.
Check whether the water is not too cold in winter (be aware of automatic drinkers, which may not be functioning properly) or too warm in summer. Provide a salt lick to stimulate water intake and/or choose to supply electrolytes.
REHIDRAMAX
We should know how to identify signs of dehydration, for example by testing the skin fold on the shoulder, evaluating the moisture of the mucous membranes, checking for dry feces, among others.
Avoid large meals before exercise
Large meals (concentrated feed, hay, or a combination of both) in the 2 hours preceding intense physical activity should be avoided, as food intake leads to a decrease in plasma volume. This decrease is due to fluid mobilization to the gastrointestinal tract, which can compromise circulatory volume and thermoregulation during exercise, increasing susceptibility to fatigue.
However, it is worth noting that horses engaged in prolonged efforts, such as endurance, benefit from prior intake of long fiber. These horses lose large amounts of water and electrolytes through sweating, and the intestinal compartments act as reservoirs for their replacement.
Prioritize fiber-rich diets
Diets high in non-structural carbohydrates (starch and sugars), consumed up to 3 hours before exercise, promote rapid carbohydrate consumption and reduce fat oxidation, which may result in premature fatigue in horses subjected to prolonged efforts (such as in Endurance and the Cross-Country phase of Eventing). Feeds low in starch and sugars are therefore preferable.
High-fiber diets appear to be beneficial for horses subjected to both short, intense efforts and prolonged exertion. These diets are also associated with higher water intake and, consequently, better hydration.
Increase fat incorporation into the diet
Fat-rich diets allow for a higher concentration of circulating fatty acids, favoring this energy pathway. This helps to preserve muscle glycogen stores, which appears to play a role in preventing fatigue.
It is important to emphasize, however, that horses must be adapted to high-fat diets. Studies show that the minimum period for these adaptive changes to begin is 3 to 5 weeks (with 10 to 12 weeks needed for full adaptation).
Ensure adequate electrolyte replacement
Horses subjected to competitive effort invariably lose water and electrolytes through sweat. Electrolytes are essential for maintaining acid-base balance, osmoregulation, nerve impulse transmission, and muscle contraction. Significant electrolyte losses negatively affect the horse's performance, contributing to early fatigue.
