> should not be used as a growth promoter and only used to help sick animals

The issue is that a lot of animals get sick from being crammed together in small areas, unable to move, while living in their own feces and urine. If we regulated animal treatment better and required certain living conditions for animals they wouldn't get sick nearly as often and wouldn't need nearly as many antibiotics.

As it stands, regulating antibiotics to be used only on sick animals wouldn't change much since an incredibly large percentage of livestock are often sick (as a consequence of living conditions).