This is not the Prisoner's Dilemma - the "prisoners" are allowed to talk to each other and coordinate in this case. Say all the farmers in the US sign an agree

This is not the Prisoner's Dilemma - the "prisoners" are allowed to talk to each other and coordinate in this case. Say all the farmers in the US sign an agreement not to use antibiotics. They also pay a small fee for policing this agreement amongst themselves to make sure that nobody is cheating. This gives a result completely different from that of the Prisoner's Dilemma.