That's a great question, and a great topic to use the search function for.
Run a search and read all of the past responses on the subject.
The problem is that this question has been asked so many times that a LOT of really qualified and experienced members won't respond again.
I am not being short, rude, or disrespectful to you AT ALL. I just want you to get the best possible information.
We keep our cooler set at 45 degrees, until about a week before they go to the show. Then we start warming them up.
When they go into the cooler, they get some Precon or Receiving Chow which has some medication in it. I believe that it keeps them from getting sick due to the temperature fluctuations that they are exposed to.