"enslaved" and "misery" are not words which are applicable.

Regardless of the day to day treatment of animals (which is only even "acceptable" in a tiny minority of places[1]), they are still bred to meet our needs and killed long before the end of their natural life. You shouldn't be measuring the treatment of the animals you eat relative to awful treatment they experience elsewhere in the world, you should measure it relative to the life the animals would lead naturally [edited from "in the wild"]. Animals killed for meat are usually slaughtered very early on in their life, long before they've lived 10% of what they would live naturally [edited from "in the wild"].

[1] Factory farming is near 99% of all livestock farming in the USA.