In the rare circumstance when there is no supply of grains, the government may sanction the eating of meat.

“In a rare circumstance when there is no supply of grains, the government may sanction the eating of meat. However, when there is sufficient food, the government should not allow the eating of cow’s flesh just to satisfy the fastidious tongue. In other words, in rare circumstances, when people are suffering for want of grains, meat-eating or flesh-eating can be allowed, but not otherwise. The maintenance of slaughterhouses for the satisfaction of the tongue and the killing of animals unnecessarily should never be sanctioned by a government.

As described in a previous verse, cows and other animals should be given sufficient grass to eat. If despite a sufficient supply of grass a cow does not supply milk, and if there is an acute shortage of food, the dried-up cow may be utilized to feed the hungry masses of people. According to the law of necessity, first of all, human society must try to produce food grains and vegetables, but if they fail in this, they can indulge in flesh-eating, otherwise not. As human society is presently structured, there is sufficient production of grains all over the world. Therefore the opening of slaughterhouses cannot be supported. In some nations, there is so much surplus grain that sometimes extra grain is thrown into the sea, and sometimes the government forbids further production of grain. The conclusion is that the earth produces sufficient grain to feed the entire population, but the distribution of this grain is restricted due to trade regulations and a desire for profit. Consequently, in some places, there is a scarcity of grain and in others profuse production. If there were one government on the surface of the earth to handle the distribution of grain, there would be no question of scarcity, no necessity to open slaughterhouses, and no need to present false theories about over-population.

Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), Srimad Bhagavatam, Fourth Canto, Chapter 17 – Text 25