I believe the midwestern deer are larger due primarily to the rotation of the high carb/high protien crops the farmers plant. If a deer has good genetics, and has quality food (primarily corn & beans) to feed on all year, they can put on and retain their body fat needed during the winter. The nutrients from these high quality food sources allow the antlers to grow to full potential. I also believe the midwestern states (Iowa/Illinois/Missouri/Kansas) do a much better job of managing their deer herd, therefore the bucks are gonna reach an older age class than what we typically see here.
There are many theories, but that is my $.02. They sure are fun to hunt. Hope I am fortunate enough to keep going back to Illinois every year. I love the rut in the midwest!
