I have been feeding Nutro Natural Choice for 14 years now and have a 72lb Standard Aussie and 68lb German Shepherd--ages 13 & 14 that are thriving--picture perfect coats, joints, vision, energy--I thought I would try the Ultra to better them..........HOWEVER--ULTRA DOES NOT CUT IT WITH MY DOGS.  After 6 mths on this food--I couldn't understand why my Standard Aussie SMELLED SO BAD.  The only change was the food--so I switched back........and voila--the scent is gone!  She smelled like FISH--perhaps her body couldn't metabolize the fish?  Anyone else notice this?  Since back on Natural Choice--all is well.......and clean smelling again!