To clarify, I'm not feeding my dogs differently because they are show/performance dogs; I'm feeding them differently because that is what works for the individual. Where I see feeding a dog differently because it is a performance/working dog (NOT a conformation/show dog) is where the dog is burning TONS of calories. Examples would be a working border collie/kepie or, perhaps, a greyhound that is being run many times a week (I don't know how they work things at the track), a working military/border patrol dog that is logging in miles of work daily, etc. My performance/show dogs are more weekend warriors by comparison. Training less than an hour everyday (not that I really train 7 days a week), hardly needs a special diet (IMHO).
I will say I feed the basenjis more in the winter than the summer; they need more calories when it's cold. I also cook an egg on show/agility/coursing mornings, but that's because Digital is a picky boy and I need him to having something in his tummy when he's performing in agility/coursing. And it has just sort of carried over even though Miss Zest would never turn down food of any sort. Of course that's not too different from most weekends since I usually cook a big breakfast on Sat and Sun and everyone gets a bite of egg then.
However, I will say I know of some people who do feed their current show dogs a better diet than the non-show dogs, which I find very sad.
Well put, especially your last comment… I totally agree.... and pets/companions deserve the best we can feed them... no different then show/performace dogs...