Srimad Bhagavatam Canto Three Chapter Two Verse Twenty Nine
As He grew to six and seven years old, the Lord was given charge of looking after the cows and bulls in the grazing grounds. He was the son of a well-to-do landholder who owned hundreds and thousands of cows, and according to Vedic economics, one is considered to be a rich man by the strength of his store of grains and cows. With only these two things, cows and grain, humanity can solve its eating problem. Human society needs only sufficient grain and sufficient cows to solve its economic problems. All other things but these two are artificial necessities created by man to kill his valuable life at the human level and waste his time in things which are not needed. Lord Krsna, as the teacher of human society, personally showed by His acts that the mercantile community, or the vaisyas, should herd cows and bulls and thus give protection to the valuable animals. According to smrti regulation, the cow is the mother and the bull the father of the human being. The cow is the mother because just as one sucks the breast of one's mother, human society takes cow's milk. Similarly, the bull is the father of human society because the father earns for the children just as the bull tills the ground to produce food grains. Human society will kill its spirit of life by killing the father and the mother. It is mentioned herein that the beautiful cows and bulls were of various checkered colors--red, black, green, yellow, ash, etc. And because of their colors and healthy smiling features, the atmosphere was enlivening.