It happens to us all. Either we get careless and exterminate all the animals near our base, or perhaps there weren't a lot there to begin with and we have to search the land for some animals. We grab us some wheat and go find the three sheep grazing half a click away. And then we commence the day-long task of manually herding the animals back to our fields. And we know how easily they get distracted, especially that one sheep that lags behind a bit because he saw a turtle for the first time or something.
Here's where your dog comes in! You get out your trusty Stick, crafted with an easily gathered two planks of wood! Tap your dog, then tap the ground where you want him to gather up all the sheep he can find! He runs around the backside of them and the sheep get moving! He'll keep it up as long as you have the Stick in hand. Tap another spot on the ground, and he'll take them there.
I don't know about you, but I can never find the slime ball needed by competitors for crafting their expensive animal leads. It's great for bringing animals home from afar.