One who muzzles an animal and threshes with it receives lashes and must pay four cavs (6 liters) for a cow and three kavs for a donkey. But why should it be so? The rule is that one does not receive lashes and pay money for the same crime!
The proof is from the case of a son consorting with his mother who is a harlot. Since the son is liable to the death penalty for incest, he is not obligated to pay, and the sheep that he gave her should be considered a present, not a payment. Since the Torah forbade that sheep as a sacrifice, it must be that he is legally obligated to pay, only that it is unenforceable in court. So too in the case of muzzling.