Depends on the type of frog for it to be actually poisonous to them, because my mom's friend's cat ate one and got a mouth infection and died. The cheeks on the side of their face if you carefully squeeze them a white liquid will come out, this is their defense. It makes the predators mouth sticky and taste bad.
When I was a kid we had lots of those little frogs that live around water troughs and our chickens ate them left and right. Frogs attract snakes so we were happy that the chickens took care of the snake food. I don't know what kind of frogs they were. Just little frogs about the size of your thumb tip.