If one finds an animal's in a barn... when is one obligated to return it to the owner of the barn. Plus, a kohen doesn't have to become impure for returning a lost object. Plus, nobody needs to listen to parents who are instructing their children not to follow through on a Torah commandment. Also, take the burden off the overloaded animal. Also, "tza'ar ba'alei chayim" - the prohibition against causing harm to animals. But if the animal's well-being is the issue, what happens when there's also monetary loss? That is, once the values are competing, which takes priority? What about the biblical vs. rabbinic level of concern?