Prohibits synthetic amino acids
Chickens are naturally omnivorous, and insects, worms, and even small animals are a part of their natural diet. When chickens are confined indoors and given a vegetarian diet, they require additional amino acids (the building blocks of protein) for proper growth. Rather than achieving adequate levels of amino acids in the chicken's diet by allowing outdoor access -- where the chicken can forage for insects and worms -- and/or supplementing with natural sources of amino acids, chicken feed producers routinely add synthetic amino acids to the feed.
Prohibits synthetic amino acids: How labels stack up against criteria