Male cows, also known as bulls, do not have udders. Udders are a specialized structure of the mammary glands of female cattle, analogous to breasts on a human being.
The udder consists of four glands grouped together into a single organ. Each gland has a long teat, analogous to a nipple, which drains the gland when suckled by a calf or milked by a farmer. Bulls do not have udders because this structure develops based upon exposure to high levels of estrogen when the female animal becomes sexually mature. Female cows have estrogen-based endocrine systems, which leads to their bodies becoming sexually differentiated from bulls at puberty.