The FDA rules left a number of loopholes. Overall usage has declined and in some cases quite substantially, but they're still being misused. For instance animals can still be given antibiotics as a 'preventative measure.' In 2017, there were still 2.3 million kg of antibiotics sold for usage in cattle alone. [1] To try to give that number some context there are about 95 million head of cattle in the US, so that works out 24g per cow per year even at the current reduced rate.

Actually creates quite a sick motivation system if the FDA does close the loopholes. Growers would have an incentive for their animals to develop conditions requiring antibiotics, so long as it did not significantly risk the animal's health.

[1] - http://www.cidrap.umn.edu/news-perspective/2018/12/fda-repor...