SB 10.5.26

For human happiness, one must care for the animals, especially the cows. Vasudeva therefore inquired whether there was a good arrangement for the animals where Nanda Mahārāja lived. For the proper pursuit of human happiness, there must be arrangements for the protection of cows. This means that there must be forests and adequate pasturing grounds full of grass and water. If the animals are happy, there will be an ample supply of milk, from which human beings will benefit by deriving many milk products with which to live happily. As enjoined in Bhagavad-gītā (18.44), kṛṣi-go-rakṣya-vāṇijyaṁ vaiśya-karma-svabhāvajam. Without giving proper facilities to the animals, how can human society be happy? That people are raising cattle to send to the slaughterhouse is a great sin. By this demoniac enterprise, people are ruining their chance for a truly human life. Because they are not giving any importance to the instructions of Kṛṣṇa, the advancement of their so-called civilization resembles the crazy efforts of men in a lunatic asylum.