Head over to Turnipseed Farm. This challenge makes you throw cows into a blue abduction beam and you get bonus points if the cow is alive, which you will need. When doing this challenge, the farmers will begin shooting at you. If you have already upgraded your shields, ignore these farmers, as they will do little damage.
Just follow the blue beam foot and throw all cows into it. It may take you two tries, one to learn the route and one to actually execute the abducting. All of the cows are really close to the beam, so just stay close to it. Look for fences, as the cows are normally in those.