The vaiśyas, the members of the mercantile communities, are especially advised to protect the cows. Cow protection means increasing the milk productions, namely curd and butter. Agriculture and distribution of the foodstuff are the primary duties of the mercantile community backed by education in Vedic knowledge and trained to give in charity. As the kṣatriyas were given charge of the protection of the citizens, vaiśyas were given the charge of the protection of animals. Animals are never meant to be killed. Killing of animals is a symptom of barbarian society. For a human being, agricultural produce, fruits and milk are sufficient and compatible foodstuffs. The human society should give more attention to animal protection. The productive energy of the laborer is misused when he is occupied by industrial enterprises. Industry of various types cannot produce the essential needs of man, namely rice, wheat, grains, milk, fruits and vegetables. The production of machines and machine tools increases the artificial living fashion of a class of vested interests and keeps thousands of men in starvation and unrest. This should not be the standard of civilization.
(Srimad Bhagavatam-----1:9:26-----purport).

Cow slaughter is an act of the grossest type of ignorance. In the Vedic literature (Ṛg Veda 9.46.4) the words gobhiḥ prīṇita-matsaram indicate that one who, being fully satisfied by milk, is desirous of killing the cow is in the grossest ignorance. There is also a prayer in the Vedic literature that states:
namo brahmaṇya-devāya
go-brāhmaṇa-hitāya ca
jagad-dhitāya kṛṣṇāya
govindāya namo namaḥ
"My Lord, You are the well-wisher of the cows and the brāhmaṇas, and You are the well-wisher of the entire human society and world." (Viṣṇu Purāṇa 1.19.65) The purport is that special mention is given in that prayer for the protection of the cows and the brāhmaṇas. Brāhmaṇas are the symbol of spiritual education, and cows are the symbol of the most valuable food; these two living creatures, the brāhmaṇas and the cows, must be given all protection—that is real advancement of civilization. In modern human society, spiritual knowledge is neglected, and cow killing is encouraged. It is to be understood, then, that human society is advancing in the wrong direction and is clearing the path to its own condemnation. A civilization which guides the citizens to become animals in their next lives is certainly not a human civilization.
(Bhagavad-Gita-----14:16-----purport).

The Lord is the protector of cows and the brahminical culture. A society devoid of cow protection and brahminical culture is not under the direct protection of the Lord, just as the prisoners in the jails are not under the protection of the king but under the protection of a severe agent of the king. Without cow protection and cultivation of the brahminical qualities in human society, at least for a section of the members of society, no human civilization can prosper at any length.
(Srimad Bhagavatam-----1:14:34-----purport).

The principal sign of the age of Kali is that lower-caste śūdras, i.e., men without brahminical culture and spiritual initiation, will be dressed like administrators or kings, and the principal business of such non-kṣatriya rulers will be to kill the innocent animals, especially the cows and the bulls, who shall be unprotected by their masters, the bona fide vaiśyas, the mercantile community. In the Bhagavad-gītā (18.44), it is said that the vaiśyas are meant to deal in agriculture, cow protection and trade. In the age of Kali, the degraded vaiśyas, the mercantile men, are engaged in supplying cows to slaughterhouses. The kṣatriyas are meant to protect the citizens of the state, whereas the vaiśyas are meant to protect the cows and bulls and utilize them to produce grains and milk. The cow is meant to deliver milk, and the bull is meant to produce grains. But in the age of Kali, the śūdra class of men are in the posts of administrators, and the cows and bulls, or the mothers and the fathers, unprotected by the vaiśyas, are subjected to the slaughterhouses organized by the śūdra administrators.
(Srimad Bhagavatam-----1:17:1-----purport).

Progressive human civilization is based on brahminical culture, God consciousness and protection of cows. All economic development of the state by trade, commerce, agriculture and industries must be fully utilized in relation to the above principles, otherwise all so-called economic development becomes a source of degradation. Cow protection means feeding the brahminical culture, which leads towards God consciousness, and thus perfection of human civilization is achieved. The age of Kali aims at killing the higher principles of life, and although Mahārāja Parīkṣit strongly resisted the domination of the personality of Kali within the world, the influence of the age of Kali came at an opportune moment, and even a strong king like Mahārāja Parīkṣit was induced to disregard the brahminical culture due to a slight provocation of hunger and thirst. Mahārāja Parīkṣit lamented the accidental incident, and he desired that all his kingdom, strength and accumulation of wealth would be burned up for not being engaged in brahminical culture, etc.
Where wealth and strength are not engaged in the advancement of brahminical culture, God consciousness and cow protection, the state and home are surely doomed by Providence. If we want peace and prosperity in the world, we should take lessons from this verse; every state and every home must endeavor to advance the cause of brahminical culture for self-purification, God consciousness for self-realization and cow protection for getting sufficient milk and the best food to continue a perfect civilization.
(Srimad Bhagavatam-----1:19:3-----purport).

The mercantile class is also required to give protection to the cows in order to get sufficient milk and milk products, which alone can give the proper health and intelligence to maintain a civilization perfectly meant for knowledge of the ultimate truth.
(Srimad Bhagavatam-----2:5:37-----purport).

A person who is situated in the mode of goodness is certainly more intelligent than others. Therefore he can practice the brahminical activities—namely speaking the truth, controlling the senses, controlling the mind, remaining always clean, practicing tolerance, having full knowledge about one's self-identity, and understanding devotional service. In this way, if he engages himself in the loving service of the Lord as an actual brāhmaṇa, his aim to achieve the final interest of life is attained. Similarly, the kṣatriya's duties are to give protection to the citizens, to give all his possessions in charity, to be strictly Vedic in the management of state affairs and to be unafraid to fight whenever there is an attack by enemies. In this way, a kṣatriya can satisfy the Supreme Personality of Godhead by his occupational duties. Similarly, a vaiśya can satisfy the Supreme Godhead by properly executing his occupational duties—engaging himself in producing foodstuffs, giving protection to cows, and trading if necessary when there is an excess of agricultural production.
(Srimad Bhagavatam-----4:21:33-----purport).

The śāstra especially recommends, kṛṣi-go-rakṣya: the vaiśya section of humanity should arrange for the food of the entire society through agricultural activities and should give full protection to the cows, which are the most useful animals because they supply milk to human society.
(Srimad Bhagavatam-----6:4:9-----purport).

One cannot become spiritually advanced without acquiring the brahminical qualifications and giving protection to cows. Cow protection insures sufficient food prepared with milk, which is needed for an advanced civilization.
(Srimad Bhagavatam-----6:18:52-----purport).

In Vedic culture, the welfare of the cows and the welfare of the brāhmaṇas are essential. Without a proper arrangement for developing brahminical culture andprotecting cows, all the affairs of administration will go to hell.
(Srimad Bhagavatam-----7:3:13-----purport).

In Kali-yuga, instead of drinking milk, people prefer to slaughter an animal and eat its flesh. The Supreme Personality of Godhead, in His instructions of Bhagavad-gītā, advises go-rakṣya, which means cow protection.
(Srimad Bhagavatam-----8:6:12-----purport).

The cow should be protected, milk should be drawn from the cows, and this milk should be prepared in various ways. One should take ample milk, and thus one can prolong one's life, develop his brain, execute devotional service, and ultimately attain the favor of the Supreme Personality of Godhead. As it is essential to get food grains and water by digging the earth, it is also essential to give protection to the cows and take nectarean milk from their milk bags.
(Srimad Bhagavatam-----8:6:12-----purport).

The so-called vaiśyas—the industrialists or businessmen—are involved in big, big industrial enterprises, but they are not interested in food grains and milk. However, as indicated here, by digging for water, even in the desert, we can produce food grains; when we produce food grains and vegetables, we can give protection to the cows; while givingprotection to the cows, we can draw from them abundant quantities of milk; and by getting enough milk and combining it with food grains and vegetables, we can prepare hundreds of nectarean foods. We can happily eat this food and thus avoid industrial enterprises and joblessness.
(Srimad Bhagavatam-----8:6:12-----purport).

Agriculture and cow protection are the way to become sinless and thus be attracted to devotional service. Those who are sinful cannot be attracted by devotional service.
(Srimad Bhagavatam-----8:6:12-----purport).

When Lord Kṛṣṇa appeared, He purposefully became a cowherd boy and showed personally how to give protection to the cows and calves. Similarly, He showed respect to Sudāmā Vipra, a real brāhmaṇa. From the Lord's personal activities, human society should learn how to give protection specifically to the brāhmaṇas and cows. Then the protection of religious principles, fulfillment of the aim of life and protection of Vedic knowledge can be achieved.
(Srimad Bhagavatam-----8:24:5-----purport).

Brāhmaṇas are beautiful when they are forgiving, kṣatriyas when they are heroic and never retreat from fighting, vaiśyas when they enrich cultural activities andprotect cows, and śūdras when they are faithful in the discharge of duties pleasing to their masters.
(Srimad Bhagavatam-----9:15:40-----purport).

If we really want to cultivate the human spirit in society we must have first-class intelligent men to guide the society, and to develop the finer tissues of our brains we must assimilate vitamin values from milk. Devotees worship Lord Śrī Kṛṣṇa by addressing Him as the well-wisher of the brāhmaṇas and the cows. The most intelligent class of men, who have perfectly attained knowledge in spiritual values, are called the brāhmaṇas. No society can improve in transcendental knowledge without the guidance of such first-class men, and no brain can assimilate the subtle form of knowledge without fine brain tissues. For such important brain tissues we require a sufficient quantity of milk and milk preparations. Ultimately, we need to protect the cow to derive the highest benefit from this important animal. The protection of cows, therefore, is not merely a religious sentiment but a means to secure the highest benefit for human society.
(Light of the Bhagavata).

Less intelligent people underestimate the value of cow's milk. Cow's milk is also called gorasa, or the juice from the body of the cow. Milk is the most valuable form of gorasa, and from milk we can prepare many important and valuable foodstuffs for the upkeep of the human body. The killing of cows by human society is one of the grossest suicidal policies, and those who are anxious to cultivate the human spirit must turn their attention first toward the question of cow protection.
(Light of the Bhagavata).

Protection and grazing ground for the cows are among the essential needs for society and the welfare of people in general. The animal fat required for the human body can be well derived from cow's milk. Cow's milk is very important for human energy, and the economic development of society depends on sufficient food grains, sufficient milk, and sufficient transportation and distribution of these products. Lord Śrī Kṛṣṇa, by His personal example, taught us the importance of cow protection, which is meant not only for the Indian climate but for all human beings all over the universe.
(Light of the Bhagavata).