For 60 years, US factory farms have included broad-spectrum antibiotics in the feed for livestock. It is said to promote growth. It also promotes antibiotic resistance. Fully 80% (30 million pounds) of the antibiotics used in the US are fed to animals who provide our meat and dairy products. In 1977, FDA announced it planned to withdraw approval for some antibiotic use in animal feed. It never did, till last year.
Cheap production methods introduce bacterial contamination to meat. See this Bloomberg report on pork production, and the effects of FDA's reduced inspections.
Some claim farmers will be able to use the drugs for "disease prevention." How FDA enforces this change will determine its scope.
Kudos to FDA for the very important decision. Let's hope this time it sticks. Banning antibiotics in feed may increase the price of food a little. But the quality of the US food supply, especially its factory-farmed meat, is currently so poor, that efforts to turn around the degradation of the food supply, and begin improving the quality of our foodstuffs are really important. Hopefully, FDA will next ban the use of arsenic and prozac in chickens , as well.