A discussion for the fun of it on this subject via Unqualified Offerings.
My thoughts – animals are basically our responsibility. Similar to babies. Babies we can force to sleep on the floor and eat almost sour milk and pinch them in the cheeks. But at some point a line will be crossed and that baby will be taken away (hopefully) because you’ve crossed the line.
Same for animals. Like babies, they don’t know we essentially “own” them. They know who butters their bread and what choices they have within the confines (word corrected) of their “homes”. And they make do. Slaughter isn’t inherently “cruel” and any of Temple Grandin’s books will have you seeing that. (designer of about 1/2 the slaughter houses in the US)
Is there a libertarian argument against animal cruelty? Only if there is one against child cruelty. And I suspect there is.
The more you know of animals and are able to read them, the more you realize that they too have “life” and thoughts and personality quirks etc. The less you know, the less you see. Hence, rats are less close to us than dogs. Yet those who know birds realize how unique each one is. That uniqueness is what once was thought of as a “human trait”, so the more you see it, the more “human” or worthwhile each creature is.