To get clarified butter, milk is necessary. Milk is produced when there are sufficient cows. Therefore in Bhagavad-gita cow protection is recommended. Great sages who were completely aware of the Vedic ritualistic ceremonies took charge of that surabhi cow, which produced all the yogurt, milk and ghee absolutely necessary for offering oblations into the fire. They wanted this pure ghee for the performance of sacrifices to elevate themselves to the higher planetary systems, up to Brahmaloka.