Mark Zuckerberg - when he's not building Facebook - likes to give himself personal challenges to learn something about the world, expand my interests and teach myself greater discipline, he recently told a magazine.

For example, last year his Challenge was to learn Chinese, giving himself an hour a day to do it.

It has been a very humbling experience, he said in an e-mail to Fortune published on Thursday. You just need to practice and practice.

He said he has traveled to the country, learned about its culture and history and met a lot of interesting new people.

His latest personal challenge revolves around being thankful for the food I have to eat. Zuckerberg says he has started to slaughter the meat that he eats. A hint of his practice was revealed publicly on May 4 in a Facebook posting where he wrote I Just killed a pig and a goat.

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, Zuckerberg told Fortune in an e-mail on Thursday.

His way for doing that has meant that he has basically become a vegetarian since the only meat I'm eating is from animals I've killed myself.

He says it that so for it has been a good experience noting he's eating healthier foods and has learned about sustainable farming and raising of animals.

When did the seed for this come about?

He started thinking about it at a pig roast at his house last year. Many people there told him they liked the meat bu didn't want to think about the fact that the pig had once been alive.

That just seemed irresponsible to me, he said. 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.

Zuckerberg says he first killed a lobster, which was then boiled alive and told Fortune that it was difficult emotionally.

The most interesting thing was how special it felt to eat it after having not eaten any seafood or meat in a while, he said.

He later killed a chicken.