Feed once a day about 60 to 90 minutes after you are done for the day.
You may want to try a maltodextrin supplement immediately after the hunt. I use Annamaet Glycocharge from
www.lcsupply.com or howlingdogalaska.com also has a different brand.
Also, the other guys had good advice. Next, year if you are switching to a high protein high fat food do it six weeks before hunting season.
Purina did a study on sled dogs a couple of years ago that outlined the high protein & fat diet, the maltodextrin, and the feeding once a day. People much smarter than I am came up with it.
I was able to hunt my 100 plus pound chessie (not exactly built for pheasant hunting) for 10 days straight in SD. This was public land well into the season so there were no quick limits. This was a couple years ago when he was 5. He held up great and was still ranging well out at sunset on the last day.
Preseason conditioning and weight control are your best bets. Nothing will improve performance as much as that but the other stuff does help if you've done your preseason stuff.