Ugh. So there were no actual chickens? So, there's the answer as to why the guy changed his story. If he was attacked in some way, where are the injuries? Sadly, I'm afraid people who were raised not to care about the well-being of animals cannot be rehabilitated. Regardless of what happens, he will never change his attitude.
Never mind the statistical findings that animal abusers are five times as likely to commit violence against humans.
Yikes.