The answer is "trampled be".
Here's why:
* The riddle is a play on words. It's designed to make you read "trampled be" as a single phrase.
* The correct reading is "trampled, be". This means the antelope, while getting dressed, got trampled and then *became* a herd of buffalo (likely through some fantastical or absurd event).
Let me know if you'd like to try another riddle!