Someone mentioned a technique others use to quickly cool off game such as pronghorn or deer is to freeze water in plastic milk jugs, carry the frozen block of ice in an ice chest on the hunt, and put the frozen block of ice in the body cavity of the beast after field dressing. I suppose placing a bag of ice cubes from the convenience store in the body cavity would have much the same effect if you didn't have access to a freezer, such as a non-resident hunter staying in a hotel. Seems like a good idea to me.