Milk is a nutritional liquid that is a biological secretion of mammals' mammory glans, including the human species, intended for the feeding of their newborns. It consists of 83-87% water, 3.5% proteins (casein, lactalbumin), 4.8% milk fat and 3.6% fat and contains a number of vitamins and elements such as calcium, phosphorus (building materials for the skeleton), potassium, vitamins A, D and B. It comes from several animals, eg cow, goat, sheep, horse, camel, buffalo, donkey, etc. and is divided into different types according to the following criteria: taste, reinforcement, processing, breeding or production method, origin (animal/vegetable), maintenance, packaging and composition.
People initially learned to consume regular milk from other mammals after animal domestication during the Neolithic Revolution or the development of agriculture. This evolution occurred independently in different parts of the world from 9000-7000 BC, in Mesopotamia until 3500-3000 BC in America. From Southwestern Asia, domestic dairy animals have spread to Europe (starting around 7000 BC but not reaching Britain and Scandinavia until 4000 BC) and South Asia (7000-5500 BC). Pastoral nomadic economies, based mainly or exclusively on domestic animals and their products rather than on cultivation, developed as European farmers moved to the steppe of the Pontus-Caspian region in the fourth millennium BC and then spread over much of the Eurasian steppe. Sheep and goats were imported to Africa from Southwest Asia, but African cattle may have been tamed independently around 7000-6000 BC. Camels, domesticated in central Arabia in the fourth millennium BC, also have been used as dairy animals in North Africa and the Arabian Peninsula, while in the rest of the world (eg East and South East Asia, America and Australia) milk and dairy products have not historically been an important part of the diet. The increase in the urban population, coupled with the expansion of the rail network in the mid-19th century, revolutionized milk production and supply. Milk trade grew slowly in the 1860s but underwent a period of far-reaching structural changes in the 1870s and 1880s. Urban demand began to grow as consumer purchasing power grew and milk was considered to be a necessary daily commodity. The United States, India, China and Brazil are the world's largest exporters of milk and dairy products, while by 2016 China and Russia have been the largest importers of milk and dairy products worldwide and are now self-sufficient, there is a situation of overproduction of milk in several countries where production constraints are now in place.
Dairy products are products made from milk, such as butter, cheese, yoghurt and ice cream. Yoghurt contains all the nutrients of milk and can be a full meal, of high nutritional value, with low calorie content, as it is rich in proteins of high biological value, in vitamin A and vitamin D. Cheese has enormous nutritional value, as Is rich in proteins, calcium, vitamin A and D, B complex vitamin and phosphorus.