The main thing a horse needs if frequently excercising is electrolytes these are vitamins and minerals that are needed because the horse is losing vitamins and minerals his/her body needs to be healthy.
Frequently exercised horses need extra minerals and grain.
Salt
calories and salt
horses that are frequently exercised need feed with higher fiber and less suger,
Extra food for energy.
they need lots jumps and they need lots of troting polls
if they are walking on a rough terrain then they will need horseshoes. these can be put on by a farrier.
Oats and grains are high energy foods, great for horses that get frequent exercize.
increased fat
on howrse the answer is increased protein and carb.
Horses are herd (groups) animals, and as such need the company of other horses or animals. Race horses frequently have "pets" that travel with them that give them the socialization and company they need. Goats and cats are popular choices.
A dose of some oats and oftenly fresh corn grain