AKMA, a vegetarian for over a decade now, points to What is the Meatrix?, a Flash animation about meat and factory farms. Don't let the fact that it's from PETA throw you off; for once, they've created something entertaining, even if you don't agree with their radical vegetarian propaganda.

anyway, what they're saying (which makes sense to me) is to not support large corporations and their unsafe farming practices.
There was a miniseries on Sci-Fi a while back (which was probably a British series originally) called "Ultraviolet". It was about a secret government agency hunting and researching vampires (or "Code V"s) in the modern day. Their fear was that the vampires, concerned that humanity was on the verge of self-destruction, were about to take over so they could control their food supply (us) like human "battery hens". Wasn't that big a conceptual leap to the Matrix's human "farms".
Brennan
When prescribing antibiotics, doctors are constantly warned not to overprescribe them, as the microbes, which can evolve quickly thanks to their rate of reproduction, will eventually develop resistance to them, redering the drugs useless. I'd hate to see animal-based bacteria do an "end run" around our human antibiotics restrictions by way of animal antibiotics.
Thankfully, some companies are listening: McDonald's recently announced that they are calling for the phase-out of the addition of antibiotics to animal feed to promote growth.