Buddhist Monastic Code Chapter 8.4 - Pācittiya: The Food Chapter

Theravadin monks are forbidden to eat the following things, among other things :

The following types of meat are unallowable: that of human beings, elephants, horses, dogs, snakes, lions, tigers, leopards, bears, and hyenas. Human beings, horses, and elephants were regarded as too noble to be used as food. The other types of meat were forbidden either on grounds that they were repulsive ("People criticized and complained and spread it about, 'How can these Sakyan-son monks eat dog meat? Dogs are loathsome, disgusting'") or dangerous (bhikkhus, smelling of lion's flesh, went into the jungle; the lions there, instead of criticizing or complaining, attacked them).

The Commentary adds three comments here: These prohibitions cover not only the meat of these animals but also their blood, bones, skin, and hide (the layer of tissue just under the skin — see AN IV.113). The prohibition against dog flesh does not include wild dogs, such as wolves and foxes, (but many teachers — including the Thai translator of the Commentary — question this point). The flesh of a half-dog half-wolf mixture, however, would be forbidden. The prohibition against snake flesh covers the flesh of all long, footless beings. Thus eels would not be allowed.

To eat human flesh entails a thullaccaya; to eat any of the other unallowable types, a dukkaṭa (Mv.VI.23.9-15). If a bhikkhu is uncertain as to the identity of any meat presented to him, he incurs a dukkaṭa if he doesn't ask the donor what it is before eating it (Mv.VI.23.9). The Commentary interprets this as meaning that if, on reflection, one recognizes what kind of meat it is, one needn't ask the donor about the identity of the meat. If one doesn't recognize it, one must ask. If one mistakenly identifies an unallowable sort of meat as allowable and then goes ahead and consumes it under that mistaken assumption, there is no offense.

Fish or meat, even if of an allowable kind, is unallowable if raw. Thus bhikkhus may not eat steak tartare, sashimi, oysters on the half-shell, raw eggs, caviar, etc. (Raw flesh and blood are allowed at Mv.VI.10.2 only when one is possessed by non-human beings (!)) Furthermore, even cooked fish or meat of an allowable kind is unallowable if the bhikkhu sees, hears, or suspects that the animal was killed specifically for the purpose of feeding bhikkhus (Mv.VI.31.14).

Source:
Buddhist Monastic Code I
Chapter 8.4
Pācittiya: The Food Chapter