Which animals are domesticated by humans for the dairy industry?

The breeding between animals of the same breed is called ..........

$A$: Bulls not selected for breeding are castrated when young and converted to bullocks. $R$: They are the main source of animal drought power in India.

In India and China,what is the approximate percentage of the world's total livestock population?

Assertion $A$: Milk is a useful product used as a valuable food.
Reason $R$: It is the fresh natural secretion of the mammary glands of female mammals for the nourishment of their young ones.
Which option is correct for Assertion $A$ and Reason $R$?

If desirable traits (genes) are accumulated,what increases?