Wheat can be a very high percentage of the diet. Additionally, wheat is on a par with corn in energy but other nutrients are higher in wheat, especially protein.
My comment was that if giving a complete feed, I wouldn't give more than 10% of wheat or anything else in addition to the feed.
A summary of the effects of replacing corn with wheat in feed manufacture.
http://www.al.gov.bc.ca/poultry/publications/documents/wheat.pdf
http://www.perennia.ca/Fact Sheets/...Reducing Feed Costs with Whole Wheat 2012.pdf
Another interesting study using wheat.
http://www.poultryindustrycouncil.ca/pdfs/factsheets/fs_79.pdf
Other studies indicate that up to 50% of the total diet can be wheat if formulas were adjusted to compensate.
All your references relate to BROILER CHICKENS not layers. So they do not totally apply.
Corn's effect on the egg yolk color is due to the carotene that chickens can't assimilate and ends up in the yolk. As it would with any plant product high in carotene.
Carotene is not the causative factor. Corn has some of the agent that causes a more yellow color but to be correct about it-
From The American Egg Board
Yolk
Yolk color depends on the hen’s diet. If a hen eats plenty of yellow-orange plant pigments called xanthophylls, the xanthophylls will be deposited in the egg yolk. Hens fed mashes containing yellow corn or alfalfa meal lay eggs with medium yellow yolks, while those eating wheat or barley yield lighter-colored yolks. A colorless diet, such as white cornmeal, produces almost colorless yolks. Natural yellow-orange substances, such as marigold petals, may be added to light-colored feeds to enhance yolk color. Artificial color additives are not permitted. Most buyers in this country prefer gold or lemon-colored yolks. Yolk pigments are relatively stable and are not lost or changed in cooking.
http://www.incredibleegg.org/egg-facts/eggcyclopedia/c/color
