This year's show season has been blown out of the water for us, so it's ironic for me to even answer this...Mingus has spent the summer fat and lazy -- until the last month, when we've been conditioning for the one show that we'll make. Scarlett has been on a weight gaining program and enjoying being a pampered baby.
Whenever I've considered my show horses' diets, I end up deciding that if it's good for them, it's good for my pasture pets, and vice versa -- although in different amounts.
All of our horses are fed LMF Showtime, free choice orchard and good quality local grass hay, beet pulp and BOSS. Approaching show time, I cut back on hay for the horse being shown (and divide it into smaller, more frequent feedings), increase the beet pulp and slightly increase the grain.
I do not cut back on their overall intakel, as I want to maintain their energy level -- a hungry, lethargic horse will neither condition nor show well.
Other than at show time, I just don't worry about hay bellies. Perhaps I'm spoiled, since my show gelding's belly disappears in a few days.