It all depends on the area you live in the world as to which mammal with mammary glands, provides milk.

Cows do provide the most milk consumed in Australia, North America and England.

Goats milk provides almost half of the milk supply in regions such as Norway, Switzerland, the Mediterranean area, Latin America and parts of Asia and Africa.

Sheep milk used by some people in Spain, the Netherlands, Italy and the Balkans.

Camel milk in the dryer regions such as the  Middle East and central Asia.

Reindeer, commonly found in the arctic region – are the main source of milk in that region.

The llama in South America is milked.

Water Buffalo in parts of the Philippines, Asia and India.

There are also milk alternatives such as Soy, Almond, Rice and Coconut milk

The nutrient content of these milks:

References: