"How is it going to end our ability to use antibiotics."
Because their widespread, indiscriminate use of antibiotics to prevent infections in feed lots leads to the bacteria rapidly developing resistance to them.
The same thing happens, to a lesser extent, when humans use antibiotics irresponsibly. e.g., buying them over the counter in Mexico and using them every time the kid has the sniffles (due to a virus, which antibiotics won't touch), or badgering a doctor for a prescription because the nipper has an ear infection (which will go away in due course).
Or starting a properly prescribed regimen of antibiotics then stopping them because you start to feel better, or sharing the pills with the boyfriend who gave you the clap because he is ashamed to go to the clinic himself.
Here is more:
Is Wikipedia too "junk science" for you? How about John Hopkins?
Here is an animated explanation of how bacteria develop resistance to antibiotics, from the FDA:
So, yeah, this is a real problem, and it is very, very serious one.