I’m feeding 2 2/3 C per day of prescription food containing 3615 kcal/kg. I’m switching to a LID diet which is higher in both protein and fat with 4100 kcal/ kg. They suggested 2 1/3 or more for a 40 lb dog. My dog is a very small GSD. I tried a straight algabraic formula based on the difference in calories but the amount seems awfully small. Any suggestions?