As interesting as it is to read about canine nutrition, and what a bunch of scientists think is best for working dogs on a whole, nothing will compare to ACTUALLY working with and watching what is best for YOUR own dog/dogs. If they thrive on a few carbs, then feed them, regardless of what science thinks to be right. Living, breathing animals i've found have individual needs, you can use these various studies as a guide, but they may need tweaking to suit your charge...j,m,o...
Yokel.
P.S. I always found good bloody beef, greens and brown rice worked with my lot...