What should you never feed to chickens?

Several foods are genuinely toxic to chickens, including avocado (especially the skin and pit), raw or dried beans, green potatoes or tomato leaves, onions, chocolate, and anything moldy or rotten.

Most of these foods contain compounds that directly damage a chicken's system — avocado contains persin, which causes heart and respiratory failure; raw beans contain phytohaemagglutinin, a lectin that is acutely toxic even in small amounts; and solanine in green potato flesh and nightshade leaves can cause neurological damage. Moldy feed is a broad category to treat seriously, since multiple molds produce mycotoxins that accumulate in tissue and suppress immune function.

• Avocado flesh, skin, and pit all contain persin — toxic to chickens at any dose.
• Raw or dried kidney beans contain phytohaemagglutinin; as few as 3–4 beans can be lethal.
• Green potato flesh and all parts of tomato and potato plants contain solanine, a toxic alkaloid.
• Onions contain thiosulfate, which destroys red blood cells and causes hemolytic anemia in chickens.
• Moldy or rotting feed can carry mycotoxins that accumulate in eggs and meat tissue.