Antibiotics in Animal feed

What did the FDA know? 

The US Food and Drug Administration (FDA) has been repeatedly (and rightfully) accused of ignoring the elephant in the room when it comes to antibiotic-resistant disease, namely factory farming practices where antibiotics are routinely fed to animals to promote growth.
According to the landmark “Antibiotic Resistance Threat Report” published by the CDC1 in October 2013, two million American adults and children become infected with antibiotic-resistant bacteria each year, and at least 23,000 of them die as a direct result of those infections. Even more die from complications.2  
A recent article in Rodale Magazine3 highlights what the FDA knew, and hid, about antibiotics in animal feed, thereby allowing the problem to persist and grow unchecked:
“The Food and Drug Administration (FDA) has known for more than a dozen years that use of antibiotics in factory farms is harmful to humans, yet the agency has taken no meaningful action to stem their use.
That's the conclusion of a new report4 from the Natural Resources Defense Council (NRDC), published after the environmental nonprofit collected data from the agency through a Freedom of Information Act request.
The data came from an internal review on the safety of feed additives belonging to penicillin and tetracycline classes of antibiotics. The review started in 2001 and ended—for unknown reasons—in 2010.
The findings: Twenty-six of the 30 drugs reviewed didn't meet safety guidelines set in 1973, and none of those drugs would meet the safety guidelines of today.” [Emphasis mine]

Why Did FDA Ignore Risk Factors from the Very Beginning?