My 15.3hh Hunter type does all riding club activities. He looks OK on a normal cool mix, but his feet tend to crack and I sometimes feel he lacks sparkle.
Feed 1.5kg/day Equipower Basefeed instead of the cool mix. The high levels of minerals, trace elements and quality protein should improve horn growth and the oil (7%) will give him a glossy coat. If you feel he still needs extra sparkle, add 0.5-1kg/day of Extruform, when he is working hard.