Side note: it amazes me how many egg cartons tout how the chickens were "vegetarian fed". Even sacks of chicken feed say "all vegetarian". Got news for ya (general term).... chickens are OMNIVORES!! I love watching ours chase and scratch for bugs. If the chickens aren't fed what their bodies need, then just like a pregnant woman who doesn't get the right nutrition, the egg will suffer in quality.
Won't do any good to present any studies, you won't believe them.