PURPORT

The surabhi cow is described as havirdhani, the source of butter. Butter, when clarified by melting, produces ghee, or clarified butter, which is inevitably necessary for performing great ritualistic sacrifices. As stated in Bhagavad-gita (18.5), yajna-dana-tapah-karma na tyajyam karyam eva tat: sacrifice, charity and austerity are essential to keep human society perfect in peace and prosperity. Yajna, the performance of sacrifice, is essential; to perform yajna, clarified butter is absolutely necessary; and to get clarified butter, milk is necessary. Milk is produced when there are sufficient cows. Therefore in Bhagavad-gita (18.44), cow protection is recommended (krsi-go-raksya-vanijyam vaisya-karma svabhava-jam).