I think they're both physically clean. Chicks are more messy. And we don't eat rats because they don't provide enough substantial meat. 1 chicken can feed a family and have left overs. 1 person would have to eat a few rats to be full. It's just economically better to raise chickens.
Cows are super filthy. They sit in their own feces. People eat beef no problem. So I don't think it's a matter of cleanliness when it comes to food animals in your example.
If you want to feed chicks, I don't see a problem.
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