Livestock is bred to be slaughtered. No life to be had there since they die in the end regardless and do not have good lives in the slightest (regardless of the conditions they live in), so in terms of animal welfare, it's the best possible outcome for them to not be raised at all. Take in as many of these animals in animal sanctuaries and let them live there as far as possible. But arguing that pigs, chickens etc. must be bred in order to them not getting extinct is a cruel thought. My two cents.

Edit: Plus, the livestock we know today only exists because of breeding. These are not naturally-occurring animals except for maybe chickens. Same thing that happens with dog breeds, cat breeds etc.