If an animal is staying in a particular body for so many days or so many years and is untimely killed, then he has to come back again in that form of life to complete the remaining days in order to be promoted to another species of life.

Indian Government Official: "Let them eat rats"

Why killing rats is not going to reduce the rat population

Ahimsa means not arresting the progressive life of any living entity. One should not think that since the spirit spark is never killed even after the killing of the body, there is no harm in killing animals for sense gratification. People are now addicted to eating animals, in spite of having an ample supply of grains, fruits and milk. There is no necessity for animal killing. This injunction is for everyone. When there is no other alternative, one may kill an animal, but it should be offered in sacrifice. At any rate, when there is an ample food supply for humanity, persons who are desiring to make advancement in spiritual realization should not commit violence to animals. Real ahimsa means not checking anyone's progressive life. The animals are also making progress in their evolutionary life by transmigrating from one category of animal life to another. If a particular animal is killed, then his progress is checked. If an animal is staying in a particular body for so many days or so many years and is untimely killed, then he has to come back again in that form of life to complete the remaining days in order to be promoted to another species of life. So their progress should not checked simply to satisfy one's palate. This is called ahimsa.

How to get yourself killed over and over again

"Narada Muni continued, 'All the animals that you have killed and given unnecessary pain will kill you one after the other in your next life and in life after life.'

PURPORT
This is another authoritative statement made by the great sage Narada. Those who kill animals and give them unnecessary pain—as people do in slaughterhouses—will be killed in a similar way in the next life and in many lives to come. One can never be excused from such an offense. If one kills many thousands of animals in a professional way so that other people can purchase the meat to eat, one must be ready to be killed in a similar way in his next life and in life after life. There are many rascals who violate their own religious principles. According to Judeo-Christian scriptures, it is clearly said, "Thou shalt not kill." Nonetheless, giving all kinds of excuses, even the heads of religions indulge in killing animals while trying to pass as saintly persons. This mockery and hypocrisy in human society bring about unlimited calamities; therefore occasionally there are great wars. Masses of such people go out onto battlefields and kill themselves. Presently they have discovered the atomic bomb, which is simply waiting to be used for wholesale destruction. If people want to be saved from the killing business life after life, they must take to Krishna consciousness and cease sinful activity. The International Society for Krishna Consciousness recommends that everyone abandon meat-eating, illicit sex, intoxication and gambling. When one gives up these sinful activities, he can understand Krishna and take to this Krishna consciousness movement. We therefore request everyone to abandon sinful activity and chant the Hare Krishna mantra: Hare Krishna, Hare Krishna, Krishna Krishna, Hare Hare / Hare Rama, Hare Rama, Rama Rama, Hare Hare. In this way people can save themselves from repeated birth and death and from being killed like the animals in slaughterhouses.