Everyone can understand that we drink the milk of cows and take the help of bulls in producing agricultural products. Therefore, since our real father gives us food grains and our mother gives us milk with which to live, the cow and bull are considered our father and mother. According to Vedic civilization, there are seven mothers, of which the cow is one. In any civilized human society, no one would dare kill his father and mother for the purpose of eating them. In the Christian religion also, a principal commandment is “Thou shalt not kill.” Nevertheless, Christians violate this rule; they are very expert in killing and in opening slaughterhouses. In Kṛṣṇa consciousness movement, our first provision is that no one should be allowed to eat any kind of flesh. It does not matter whether it is cows’ flesh or goats’ flesh, but we especially stress the prohibition against cows’ flesh because according to śāstra the cow is our mother.
Ref >> Srila Prabhupada Vani.