Worth reading. (Sources at the bottom)
You know what IS bad for chickens? Not enough Methionine (of whatever source).
PLEASE< PLEASE< PLEASE note that the amounts of DL-Methionine found in legally manufactured poultry feeds are not huge - literally a couple pounds per ton. We aren't talking about buying supplements of
horse powder off of Chewy or
human unregulated dietary supplements and feeding them to your birds. Nor should we be concerned about potential drug interactions with Warfarin and the like...
The dosage is still the poison.
Also true of Sodium, Water, Calcium, Potassium, Chlorine, Selenium, and dang near every other mineral and heavy metal needed in trace amounts to maintain life.