To teach by example, Sri Krishna and Lord Balram show us when They descend into this world, how important is to protect, love and serve Cows and Bulls. Krishna is known as Gopala (protector of the Cows) or Govinda (one who gives pleasure to the Cows). Lord Balram represents plowing the land for agriculture and therefore always carries a plow in His hand, whereas Krishna tends Cows and therefore carries a flute in His hand. Thus the two brothers represent krisi-raksha (protecting Bulls by engaging them in farming) and go-raksha (protecting the Cows). 10.5.20 Purport Lord Krishna says in Srimad Bhagavatam, "I can be worshiped within the Cows by offerings of grass and other suitable grains and paraphernalia for the pleasure and health of the Cows, and one may worship Me within the Vaishnavas by offering loving friendship to them and honoring them in all respects."
Kamadhenu, the sacred cow which grants all wishes and desires, is an integral part of Hindu mythology. This divine cow, which lives in swargalok (heaven), emerged from the ocean of milk (ksheerasagar) at the time of samudramanthan (the great churning of the ocean by the gods (suras) and gemons (asuras). It was presented to the seven sages by the Gods, and in course of time came into the possession of Sage Vasishta.
Kamadhenu's complexion is like the white clouds. Every part of cow's body has a religious significance. Its four legs symbolize the four Vedas, and its teats the four Purusharthas. Its horns symbolize the gods, its face symbolize the sun and the moon, its shoulders Agni (the god of fire), and its legs the Himalayas
Kamadhenu is also well-known through its other five forms: Nanda, Sunanda, Surabhi, Susheela and Sumana.
The cow symbolizes the dharma itself. It is said to have stood steadily upon the earth with its four feet
during the Satyug (world's first age of truth), upon three feet during the Tretayug (the second stage of less than perfection), upon two feet during the Dwaparyug (the third stage of dwindling and disappearing perfection) and only on one leg during Kaliyug (the fourth and current age of decadence).