The cow is very, very important animal. If you want to advance your spiritual consciousness, then you must have sufficient milk and sufficient grains. That is civilization. Therefore it is the duty of the vaisyas to produce food grain, annad bhavanti bhutani. Annad. In the society, if you have got sufficient anna, both the animals and the man, they will be happy. These are the instruction in the Bhagavad-gita, everything practical.

(Srila Prabhupada, lecture, Oct. 17, 1975)