Oxford might have an animal control officer (dog officer), and that would be the individual who should have some idea of what the rules are. Ask at the police department, since dog/animal controll officers are sometimes part of the force.
In Massachusetts, each town's animal control officer is required to annually inspect every site where livestock and poultry are kept, and keep a census of what and how many of each kind of animal you have. Then he or she sends the list (it's called a barn book) to the Mass. Dept. of Agricultural Resources, who in turn file it and make the information available to the USDA. Dogs, cats and other household pets are not part of the barn book -- dogs of course are separately registered.
Hope that helps. If you can't get anywhere in Oxford, PM me and I'll see if I can help you find out. I'm not in Oxford, but things tend to run similarly all across Mass.