LittleMsSam has a great mod that "let pets go for a walk themselves" and an add-on: "Pet needs fill up if they go for a walk" option.
You simply click on a pet, tell them to "go for a walk for 60/120180 minutes", they disappear into a rabbit hole and you get to focus on your sims until they come back from their walk.
Worked great especially for my sim Farm with 5 livestock (pets) and chickens. She also has another mod that reduces the chance of your pets getting sick, a great life saver if you have a lot of pets.
