Years ago I used to feed purina layer feed and my yolks were noticeably darker than my bird's yolks are now and they free range every day. Don't get me wrong, my yolks aren't pale, but not as dark as they were with the purina. I'd be willing to bet if you look at the ingredients it contains marigold extract or something similar to help influence yolk color.
edit: I should add that when I did feed purina I had NOT started free ranging my birds yet.
edit: I should add that when I did feed purina I had NOT started free ranging my birds yet.
