If you get it packed in ice you should be fine, here in GA we rarely have the luxury of having daytime temperatures in the 60s until well into October so getting it iced down is a major goal. Try not to allow the meat to get wet, don't wrap the meat in plastic, but try to insure that the ice is isolated from the meat by either a good solid bag or adequate drainage. There are times when it is impossible to get an animal to a cooler or cut up before the few hours mentioned by several others. Here in GA, as an example, a Bear must be checked in with the DNR before it is cut up. This must be done within 24 hours of it being killed and that can be a problem when the Ranger on duty may be miles away when you call to get somebody to check it in, especially if you have to get the dern thing out of the mountains and into the truck before you can even make the call. Pack the body cavity with as many bags of ice as you can stuff in there and pack some around the outside if you can and hope for the best.