Free: Contests & Raffles.
The field is not the dogs domain, his yard and your backyard is. If you saw a stranger approach you in a mall you wouldn't act aggressive towards that person, if that same stranger walked into your house, you would act the same as the dog, you know...trapping him, biting and chewing on him. Both my dogs will run down anything in the field if I will let them, a strong voice and/or e-collar takes care of the times I do not wish this to happen. Now, If something like a cat and rabbit or random birds lights in the backyard, it's game on.