The suffering that animals undergo while being caught and eaten may be intense and the process by which they are killed may last for a quarter of an … - Jeff McMahan

Viewed from a distance, the natural world often presents a vista of sublime, majestic placidity. Yet beneath the foliage and hidden from the distant eye, a vast, unceasing slaughter rages. Wherever there is animal life, predators are stalking, chasing, capturing, killing, and devouring their prey. Agonized suffering and violent death are ubiquitous and continuous.

[I]f suffering is bad for animals when we cause it, it is also bad for them when other animals cause it. That suffering is bad for those who experience it is not a human prejudice; nor is an effort to prevent wild animals from suffering a moralistic attempt to police the behavior of other animals. Even if we are not morally required to prevent suffering among animals in the wild for which we are not responsible, we do have a moral reason to prevent it, just as we have a general moral reason to prevent suffering among human beings that is independent both of the cause of the suffering and of our relation to the victims. The main constraint on the permissibility of acting on our reason to prevent suffering is that our action should not cause bad effects that would be worse than those we could prevent.

Suppose that we could arrange the gradual extinction of carnivorous species, replacing them with new herbivorous ones. Or suppose that we could intervene genetically, so that currently carnivorous species would gradually evolve into herbivorous ones, thereby fulfilling Isaiah's prophecy. If we could bring about the end of predation by one or the other of these means at little cost to ourselves, ought we to do it?