That has been true since the 1950s, the very beginning of the antibiotic era, and it’s only in the past decade that the practice has been seriously called into question as a matter of agricultural policy.

In the United States, the Food and Drug Administration struggled for decades to remove the smallest antibiotic doses—known as “growth promoters” because they cause animals to reach market weight faster—from meat production. It never succeeded. Last year, the agency took a different tack, creating voluntary restrictions whose primary impact is on veterinary-pharma manufacturers, but that nevertheless should reduce antibiotic use by farmers.

In Europe, though, growth promoters have been banned since 2006, and several countries have instituted additional curbs on antibiotic use. One notable case