Dosage, dosage, dosage. Practically anything we or the chickens eat contains something that can harm us or them if we eat to excess. This includes practically everything on the treats chart. You have to eat enough of that substance for it to cause harm. Some things are cumulative so it’s how much you eat over a time period, some things are expelled from the body pretty quickly so you have to eat a whole lot at one sitting.
For example, those whole potatoes so many people are concerned about. A normal healthy human adult would need to eat well over 50 pounds of white potatoes to eat enough solanine to harm themselves. Since the liver is pretty good about separating this out from your body, it would have to be at one time. Bee, if you want to off your hubby get him to eat around 60 pounds of potatoes at one sitting. That might be enough. (Bee and I know each other so I can pick on her.) Chickens are a lot smaller than humans so they would not have to eat as much, but their crops just aren’t that big. Even if they wanted to they could not eat that much. The problem with potatoes is when potatoes turn green. Solanine is concentrated in those potatoes so there is more danger. Humans should not eat green potatoes, the ones that have been sunburned. Keep those away from chickens too. By the way, cooking potatoes are normal cooking temperatures does not break down solanine and make it harmless. Avoid all green potatoes, even cooked ones.
Cabbage, one of the favorite treats on this forum, contains something that can damage the thyroid. That one is cumulative. But a normal healthy human would have to eat about 5 pounds of cabbage every day for a few weeks to see problems unless they had a bad thyroid condition to start with.
If you make a big batch of apple butter or apple cider you might wind up with a big pile of pure apple seeds. Don’t feed those to your chickens. They might get enough cyanide to harm themselves. Probably would not, but they might. But a chicken eating a few seeds in an apple core. I’m not worried about that at all.
If you are uncomfortable with any of these things, don’t feed them to start with. No one will force you to. Even if you are comfortable don’t feed to excess. Feed in moderation. Dosage, dosage, dosage.
Bee, plum pits also contain cyanide. I’ve seen plum pits in chickens’ gizzards when I butcher them. They grind those up too, just like apple seeds. It’s sometimes surprising what you can find in a chickens gizzard if you look.