Don't butcher your deer in the field, put in game bags, put game bags in PLASTIC bags to keep pack clean, then seal it all tightly while hiking out, then load closed pack in car and drive home...
...without first cooling the meat and/or taking the meat out of the pack upon arrival at the car.
I now keep a cooler in the car when hunting. Also probably a good idea to bypass the plastic bag and just wash the pack out later, especially if it's warm. Don't seal up that heat!
