The ceremony of Yagna helps one to sacrifice himself to divine and attain the power or siddhi as a fruit of the sacrifice . All these power describes by Krishna , indicates that the sadhana between this beings has got some perfection and so divine has descended in them . This is the case with all commun be it a human or animal . Each of them, when after there connectivity with soul, express the souls power in there community . In a sense all being , are doing sadhana to reach perfection . After doing the sadhana they reach such perfection like the thunderbolt , which is the most perfect form of all weapons . If you look at cow , then Surabhi looks as most perfected one – as it is a wish fulfilling cow and wish fulfilling is a common characteristics of a better quality of cow.