Some antibiotics are approved for use in animals, others in people, and still others in both animals and people (also called shared class antibiotics), but the majority of antibiotics used in animals are non-critical to human medicine.
Comparing animal and human antibiotic use is complicated. That’s why the proper context is so important.
Animals raised for food live in herds or flocks, share water and feed troughs, and seek close contact with one another by licking, laying on each other and even rubbing snouts and noses. This can spread illnesses rapidly. Waiting for animals to show symptoms of an illness before beginning treatment is often too late. Swift action can prevent the spread of disease and result in animals receiving fewer antibiotics than they would have had they not received preventive medication.