Ananda, I permit the Bhikshus to eat five kinds of pure
meat. This meat is actually a transformation brought into being
by my spiritual powers. It basically has no life-force. You
Brahmans live in a climate so hot and humid, and on such
sandy and rocky land, that vegetables will not grow; therefore,
I have had to assist you with spiritual powers and compassion.
Because of the magnitude of this kindness and compassion,
what you eat that tastes like meat is merely said to be meat; in
fact, however, it is not. After my extinction, how can those who
eat the flesh of living beings be called the disciples of Shakya?
http://online.sfsu.edu/~rone/Buddhism/Shurangama/ps.ss.02.v6.020526.screen.pdfsimple explanation by the Venerable Master Hsuan Hua
Buddha also seemed to predict that mock meats is a good alternative in present era.
There is a lot to learn from 牛that eats grass only and having such a strong and healthy body, feeding human with good quality milk as well.

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