yall are both right
except the corn and protein thing Sam. Corn is only 8% tops so it lower the protein, but adds lots of carbs and fat, which is good for winter conditioning, I do it to, just cut it off a month or so before breeding. Fat birds dont breed very well.
Animal proteins are always welcomed but best as Sam said as treats.
Mine get nothing different than any other chicken, a 15% feed is it, mixed with grain in the winter for added fat.
For showing, yes, there are show based feeds. Basically like you were saying Roger, animal proteins (especially fish based ones) are better for them on muscular and feather development, they get an over all heathier shine to them if you add in some small pellet sized cat or dog food to their diet, catfish feed would be the ideal one to use though as it is mainly fish meal based and doesnt contain beef and pork by products.
maybe 10% would be all I would add though, you can over do it and cause internal organ damage if you get crazy with the animal protein stuff (more is better attitude)
But for the most part, they do just fine on any store bought mid teen level protein feeds.
Longtailed breeds are the ones who do better on fish meals, and higher protein level feeds than any of the others due to their constant need of it for nonstop feather growth in the tails and saddles. D'anvers do well on anything pretty much