<P> Milk is a white liquid produced by the mammary glands of mammals . It is the primary source of nutrition for infant mammals (including humans who breastfeed) before they are able to digest other types of food . Early - lactation milk contains colostrum, which carries the mother's antibodies to its young and can reduce the risk of many diseases . It contains many other nutrients including protein and lactose . </P> <P> As an agricultural product, milk is extracted from non-human mammals during or soon after pregnancy . Dairy farms produced about 730 million tonnes of milk in 2011, from 260 million dairy cows . India is the world's largest producer of milk, and is the leading exporter of skimmed milk powder, yet it exports few other milk products . The ever increasing rise in domestic demand for dairy products and a large demand - supply gap could lead to India being a net importer of dairy products in the future . The United States, India, China and Brazil are the world's largest exporters of milk and milk products . China and Russia were the world's largest importers of milk and milk products until 2016 when both countries became self - sufficient, contributing to a worldwide glut of milk . </P>

Where does the milk come out of a cow