Not necessarily but it will be preferred. Since, one who eats meat
can cultivate a pure heart just as one who is vegetarian might have
an impure heart. Many people have misunderstood that Lord Buddha is
a vegetarian. This is not true since Lord Buddha consumed any kinds
of alms food offered by devotees be it meat or vegetable. One has
to understand that not all places Lord Buddha and his Sangha
travelled to, for preaching of Buddhism, has fertile lands.
Thus, the ease of obtaining meat will be much easier than
vegetable.
But, Lord
Buddha did mentioned that eating PURE meat is possible. So, how do
we define what is PURE meat? Meat ordered or received by mistake.
Leftover or discarded meat. Meat from animals that have died
naturally or by accident for at least 16 hours (The number of hours
is to ensure the consciousness has left the body). Meat from alms
rounds as practised in the Buddhist tradition.
The
Mahaparinirvana Sutta states that "...All monks who live purely and
all Bodhisattvas always refrain even from walking on grass; how can
they agree to uproot it? How then can those who practise great
Compassion feed on the flesh and blood of living beings?..."
However, Lord Buddha never made it a compulsory rule that all his
devotees have to be vegetarians, but he strongly encouraged us to
be.
The
Lankavatara Sutta states that all true practitioners of the
Bodhisattva path eventually stop meat-eating. In his previous
lives, the Buddha as a Bodhisattva would rather cut his own flesh
to feed an eagle than let it eat a dove. Thus, all advanced
practising laymen are thus necessarily vegetarians, since they
cannot bear the pain of sentient beings.