Place it as the answer in a short animal quiz, after the question and before a bell ding that marks a correct guess. Use the ding once, then let the cow stay the focus while the next animal question begins.
关于此声音
This clip is a single, clear cow moo lasting about 3.8 seconds, with no other voices or music behind it. It feels gentle and playful, like a friendly farm animal answering back, and it is easy for a small child to recognise at once. The sound is warm rather than startling, and it leaves a calm, cheerful feeling after it ends.