I think there are two directions in Christianity, in relation to animal issues: on the one hand, a general ethic of compassion, stewardship, etc. that can cover other species as well, and on the other, a view about a predetermined "order" where humans are at the top and other species at their mercy.
And likewise, an agnostic/atheist worldview can either be materialistic in the pejorative sense -- not giving any room for ideals of compassion or justice -- or then it can free us from the illusion that there are external norms ("meant to eat meat", "animals exist for us", "it's natural to eat meat") that restrict our choices, and allow us to shape our ethics in a more rational and honest way.
"and I stand
upon a mountain
made of weak and useless men"