Chickens are built to swallow large bites, including large pills. Humans have a hard time swallowing large pills because we start to digest our food by chewing. Chickens swallow before they begin their digestive process in their crops and gizzards. Even baby chicks will swallow a large "bite". Give a week-old chick a meal worm and see what happens to it. (Grit required before you try this stunt.)