Jamadagni was more powerful than Kartaviryarjuna because of performing the agnihotra-yajna with clarified butter received from the kamadhenu. Not everyone can be expected to possess such a cow. Nonetheless, an ordinary man may possess an ordinary cow, give protection to this animal, take sufficient milk from it, and engage the milk to produce butter and clarified ghee, especially for performing the agnihotra-yajna. This is possible for everyone. Thus we find that in Bhagavad-gita Lord Krsna advises go-raksya, the protection of cows. This is essential because if cows are cared for properly they will surely supply sufficient milk. We have practical experience in America that in our various ISKCON farms we are giving proper protection to the cows and receiving more than enough milk. In other farms the cows do not deliver as much milk as in our farms; because our cows know very well that we are not going to kill them, they are happy, and they give ample milk. Therefore this instruction given by Lord Krsna — go-raksya — is extremely meaningful. The whole world must learn from Krsna how to live happily without scarcity simply by producing food grains (annad bhavanti bhutani [Bg. 3.14]) and giving protection to the cows (go-raksya). Krsi-go-raksya-vanijyam vaisya-karma svabhavajam [Bg. 18.44]. Those who belong to the third level of human society, namely the mercantile people, must keep land for producing food grains and giving protection to cows. This is the injunction of Bhagavad-gita. In the matter of protecting the cows, the meat-eaters will protest, but in answer to them we may say that since Krsna gives stress to cow protection, those who are inclined to eat meat may eat the flesh of unimportant animals like hogs, dogs, goats and sheep, but they should not touch the life of the cows, for this is destructive to the spiritual advancement of human society.

Srila Prabhupada's purport to SB 9.15.25