In addition, chickens require a certain level of arsenic in their diets (NOT manmade diets, now) in order for their musculaskeletal structures to develop properly. If I had the site of the study, this might be a more interesting point - however; a study was made of chickens and several diet options, and it was reiterated that arsenic was an essential substance for their development.
The more I learn, the more I realize that I don't know much! LOL