That's what you should do if you find anything that belongs to someone else. Do whatever you can to help, whether you find a cow or sheep or donkey or some clothing.
If the owner lives too far away, or if you don't know who the owner is, take the animal home with you and take care of it. The owner will come looking for the animal, and then you can give it back.
Oxen and donkeys that carry heavy loads can stumble and fall, and be unable to get up by themselves. So as you walk along the road, help anyone who is trying to get an ox or donkey back on its feet.