Sheep have gone by with a few changes from the last game, As they become stressed from not getting brushed, And their wool grows back at a much faster rate. Other than that, you should still feed and brush the sheep every day, as well as give it love.
Sheep are a good animal to have on hand, as their wool (when at higher ranks), can give that little extra you're looking for in your pay check.
Unlocked by: Sheep, unlike cows, take time to be unlocked. The sheep are only unlocked after you have owned at least four cows. Afterwards, the sheep should be available in Mirabelle's animal shop.