Teat
One of the four milk outlets of a cow's udder, sometimes with small extra ones.
Also: dug, thann
Each quarter of the udder ends in a teat, through which milk is drawn by a calf, by hand or by a milking machine. A ring of muscle at the tip keeps milk in and germs out between milkings, and a plug of keratin forms inside the teat canal during the dry period. Many cows have small extra teats, called supernumerary teats, which are often removed while the animal is young in dairy herds. Teat length, thickness and placement are judged in dairy breeds because they affect how well a cow can be milked by machine. In many South Asian herds the calf is allowed to suckle first to start the let-down of milk before the cow is milked by hand.