It's actually the best when the ducks find one of these.
They eat plenty of earth worms, but when the find one of these it fights back, wriggling all down into the crop.
Then the others catch on and try to steal it. Chase ensues. So much fun that a visitor who witnessed it commented.
Anyway, if your chicken says "vegetarian fed", remember that chickens are not vegetarians.
They are tiny dinosaur monsters.