But this comes with costs. With limited land and intense time pressure, the solution in many countries has been to use antibiotics at scale. This isn’t just to treat illness, but also as a prophylactic to prevent disease in crowded conditions. And giving antibiotics causes livestock to grow faster, although scientists aren’t sure exactly why that is. All of this means that, unlike their use for humans – where antibiotics are almost always given to treat illness – their use in farming is much more widespread and indiscriminate. Studies tracking their use estimate that 73% of all antimicrobials sold globally are used in animals raised for food.