Cows,Pigs, Chicken etc. are used purely for the benefit of the human race (mass amounts of sustenance) if this is the case why do people consider it immoral to eat them?
#1
Ok - I don't know if this answers your question but I will tell you this anyway because it might. Livestock plays an important part in ecology, as well as feeding humans. Whatever livestock eats/ does, it effects the life of other creatures. Lets say X was livestock which ate Y. The population of Y is kept down to some degree, which helps z. Y is still existent and not suffering because of it because that is how it has adapted to be for years. But if X was gone, Y would flourish, effecting Z in a negative way. This type of thing is of butterfly effect, of course. It is basically a version of the food chain. Remove one thing, and it collapses to some degree.
Oh, and certain types of livestock help farming. Pigs can dig up fields for example. It is only recently that we replaced these helpers with machinery.
2points