World Class Nutrition,
World Class Results

Feeding the Endurance Horse Through The Winter

01 August 2006

Winter is fast approaching! For the endurance horse, riders can use this winter to get back on track and have an exceptionally fit athlete ready for the spring events.

Endurance horses are extreme athletes. As in all athletic activity of long duration, feed and fitness must go hand in hand if the horse is to perform at his best. The goal for any rider or trainer in every equine sport is to have the horse compete in top form with minimal stress.

The aim of a feeding and conditioning programme is to provide fuel reserves for the working muscles and improve muscular efficiency.

During the fittening process, the muscles, cardiovascular system, respiratory system, and neuromuscular co-ordination respond favourably to conditioning and, while you may not be able to see the changes, you will certainly see the results. A fit horse will not blow as much or tire as quickly when you are riding him, and his breathing and heart rate will return to normal more quickly after exercise. Of all the body's systems, most is probably known about how the muscles adapt during training. The extent of the alterations of the muscles during training are largely dependent on the pattern and frequency of nerve impulses arriving at the individual muscle fibres. Therefore one can only get a favourable effect from training if it entails the same type and intensity of exercise that will be encountered during competition. If the competition requires prolonged, slower speed exercise (aerobic) then the oxidative capacity of the muscles needs to be increased. Training also increases the availability of fuel to the muscle fibres by encouraging an increase in the number and size of the mitochondria within each muscle fibre. These mitochondria contain the enzymes responsible for the combustion of glucose and free fatty acids to produce energy molecules. As the horse gets fitter, in conjunction with the increase in the level of enzymes within the mitochondria, there is also an increase in the level of enzymes responsible for supplying and degrading free fatty acids before they enter the mitochondria. This results in more fatty acids being utilized, thus sparing the glycogen stores and delaying the onset of fatigue. In line with this increase in the capacity to utilize oxygen, there is also an increase in the number of small capillaries around the muscle fibres, so that the increased oxidative potential of the fibres can be properly utilized. During periods of inactivity, a reverse effect of this increased oxidative capacity is observed.

Muscles require fuel to be able to function and, therefore, the nutrition of the horse is linked to his ability to perform. What you put in not only maintains body condition but also fuels the horse, providing energy to the muscles for work. However, it is not just the amount of food that we put into a horse that is important, but also the type of food we provide. Exercise affects muscle fibre types in the horse and these muscle fibres have different contractile and metabolic characteristics, functioning under different conditions and using different fuels. Providing a diet containing alternative energy sources allows the muscles to use the most appropriate fuel for the work being done, helping to conserve precious glycogen stores. The horse has three basic muscle fibre types as shown in figure 1:

Figure 1

Different types of horses will have different percentages of muscle fibre types. (see figure 2) Figure 2

The endurance horse has more slow twitch fibres so this may explain why the Arab excels at endurance riding.

The fuel or energy that you put in is a measure of the feed's potential to fuel body functions and muscle contraction through work. As it is not possible for horses to continually eat during exercise, the energy from the feed must be stored within the body to be used later as a fuel for muscle contraction.

There are three main energy sources used by the horse. Fibre is the most important, and one that is all too commonly overlooked. As there is low enzyme activity in the saliva and in the small intestine for the digestion of sugars and starch, this suggests that the horse's main energy source is not supposed to be sugars. The primary energy source should be volatile fatty acids produced through the fermentation of forage (hay, haylage and pasture) in the hindgut by millions of bacteria. The fatty acids are then used either directly as a fuel in the cells, or they are transported to the liver and converted to fat to strengthen the body's fat stores and used for energy production later. The process is long and slow so fibre can be used as an energy source throughout an endurance event, as the fermentation of fibre continues long after the meal has been eaten. The provision of fibre is also critical to the health of any horse, as it maintains gut mobility thus reducing the occurrence of colic. Fibre also helps to maintain water intake and acts as a reservoir to hold electrolytes and water, therefore helping to prevent dehydration.

Fibre is hay, pasture and haylage but also includes products such as alfalfa, soya hulls and sugar beet. These are superior to long fibre as an energy source because their low lignin content makes them more digestible. These are important ingredients found in commercially-formulated endurance diets, such as Enduro 100, and will play an important role in increasing the energy level in the diet of the endurance horse as the new competition season approaches.

If the hindgut is fed properly with good quality fibre, the nutrients supplied are sufficient to keep most horses in light to moderate work but, as you gradually increase the speed and intensity of exercise, forage alone will not provide sufficient fuel for the muscles to function properly without fatigue. Fats are extremely energy-dense and contain up to 2.25 times more energy than the equivalent weight of cereal. Horses are able to digest fat extremely efficiently and the release of energy is slow making it an excellent energy source for horses doing prolonged low intensity exercise. Research by Pagan et al., 1987 showed that feeding fat to horses resulted in greater mobilization and utilization of fat during long distance exercise. Conditioning the horse to a high fat diet along with a sensible exercise programme takes approximately eleven weeks and results in improved enzyme systems to utilize fat, therefore sparing the use of muscle glycogen (it is actually now thought that it takes less than eleven weeks).