Crops

Enormous numbers of domesticated animals are cultivated by people as food crops. In many cases the animals are used to continuously produce some edible product that can be harvested without killing them. For example, milk can be collected daily from various species of mammals, including cows, goats, sheep, horses, and camels. Similarly, chickens can produce eggs regularly. All of the above animals, plus many other domesticated species, are also routinely slaughtered for their meat.

The populations of some of these domesticated animals are very large. In addition to approximately six billion people, the world today supports about 1.7 billion sheep and goats (Ovis aries and Capra hircus), 1.3 billion cows (Bos taurus and B. indica), 0.9 billion pigs (Sus scrofa), and 0.3 billion horses, camels, and water buffalo (Equus caballus, Camelus dromedarius, and Bubalus bubalis). In addition, there are about 10–11 billion domestic fowl, most of which are chickens (Gallus gallus).

These populations of domesticated animals are much larger than those maintained by any wild large animals. For example, no wild mammals of a comparable size to those listed above have populations greater than about 50 million, which is equivalent to less than 1% of a typical domestic-livestock population.