Tomato plants are mostly toxic just at certain times in their life, too. They don't have the same level of toxicity all of the time, from the time they sprout until the time they die. I think the plants get more toxic when the fruit is ripe. At which point, those chickens would be going after the tomatoes, more than the foliage. I'd have to try to find that information again. Maybe someone else remembers the exact details. My chickens never bother the tomato foliage, but they have lots of other things to eat when they're out. Like all my chard!
Plus, it's one thing to nibble on some things and another to feed it as a huge semi-load in a feed lot for cattle, which is where some of the toxic warnings come from, especially for things like broccoli, as a feed.

Plus, it's one thing to nibble on some things and another to feed it as a huge semi-load in a feed lot for cattle, which is where some of the toxic warnings come from, especially for things like broccoli, as a feed.