animals that part the hoof and chew the cud
Kosher animals Leviticus 11:3-8 and Deuteronomy 14:4-8 both give the same general set of rules for identifying which land animals (Hebrew: בהמות Behemoth) are ritually clean. According to these, anything that "chews the cud" and has a completely split hoof is ritually clean, but those animals that only chew the cud or only have cloven hooves are unclean.
Gizzard Birds swallow food and store it in their crop if necessary. Then the food passes into their glandular stomach, also called the proventriculus, which is also sometimes referred to as the true stomach. This is the secretory part of the stomach. Then the food passes into the gizzard (also known as the muscular stomach or ventriculus). The gizzard can grind the food with previously swallowed stones and pass it back to the true stomach, and vice versa. In layman's terms, the gizzard 'chews' the food for the bird as it does not have teeth to chew food the way humans do. Bird gizzards are lined with a tough layer made of the carbohydrate-protein complex koilin, to protect the muscles in the gizzard.