The muscle strength, character and energy required to be a winning athlete, for horses as well as humans, is partly genetic. However you can maximise genetic potential with the right training and nutrition.
While the right combination of protein, vitamins and minerals are important, calories are the key to bringing this to the fore during competition, no matter what the discipline. Grain, even oats, can help in this respect, but hard-working horses need more.
Fortunately there are many commercially prepared supplementary concentrates available that cater for all the needs of the high performing horse, designed to bring out the best in the field or arena.