Mark Zuckerberg's new challenge: eating only what he kills (and yes, we do mean literally)

Last year Mark Zuckerberg set out to learn Chinese. Now he's determined to get in touch with his food. If the goats, lobsters and chickens of Silicon Valley aren't trembling, they should be.

When he's not too busy connecting people across the universe, the Facebook founder takes on a personal challenge each year — something, as he puts it, to learn about the world and teach himself discipline. One year it was wearing a tie every day. Last year it was learning Mandarin. This year, it is dinner.

Zuckerberg has decided that the only meat he will eat is meat from animals he has killed himself. He announced it the way he announces most things: on Facebook, with a May 4 post reading, "I just killed a pig and a goat." In an email to Fortune, he explained the thinking behind it. The idea took shape at a pig roast at his house, where guests told him they loved eating pork but preferred not to dwell on the fact that the pig had once been alive. "That just seemed irresponsible to me," he wrote. "I don't have an issue with anything people choose to eat, but I do think they should take responsibility and be thankful for what they eat rather than trying to ignore where it came from."

He started small: a lobster, dispatched by boiling. Then, coached by his Palo Alto neighbor, chef Jesse Cool, he worked his way up to a chicken, a pig, and a goat. The larger animals go to a butcher in Santa Cruz, who sends the cuts back for Zuckerberg and his girlfriend Priscilla to cook as they please.

"This year I've basically become a vegetarian since the only meat I'm eating is from animals I've killed myself," he told Fortune. "I think many people forget that a living being has to die for you to eat meat, so my goal revolves around not letting myself forget that and being thankful for what I have."

Say what you will about billionaires and their hobbies. This one, at least, has a point.