Is it mandatory for a Buddhist to be a vegetarian?

Not necessarily. There are two categories of Buddhist believers, those who have joined the Buddhist sect, and most of them are vegetarians. The other category is the people who believe in Buddha, this kind of people according to their own understanding of Buddha to choose to eat vegetarian or not. Some people feel that they have to eat vegetarian to call not kill, to be pious; others believe that as long as the heart of the Buddha, wine and meat through the intestine, the Buddha's heart to stay.