Hi M & C,
Initially I wrote out how to hand calculate but the post got so long so deleted it. Hand calculating an estimated caloric value is just an extension of calculating the number of fat calories. For a G/A that lists min protein as 25 and min fat as 25 and max moisture at 10 and max fiber as 5 you can estimate carbs by subtracting the knowns from 100. If you know the ash content, you need to subtract that too, but if you don’t you can guess (Balanceit uses 3). In this example estimated carbs is 100-25-25-10-5-3= 32. Next multiply each macronutrient by number of kcals/gram, which is 4 for protein and carb and 9 for fat. For kibble I use the Modified Atwater numbers which are 3.5 kcals/gram for protein and carb and 8.5 kcals/gram for fat to accounts for digestibility. For this example (4X25) + (4X 32) + (9 X 25) = 453 kcals/100 grams= 4530kcals/kg
Estimating is fraught with error though, especially with fresh foods, which I why I use the given caloric information if it is available. What I’ve found is the underreporting of fat in raw foods is very common, this is evident if your carb number ends up high when there is no plant matter listed in the ingredients. Also, you can back calculate fat content if they give the caloric information.
Years ago, I asked a company whose name would imply that they would respond to inquiry, what the fat content was in their food. They wrote back that it took them years of research to determine the ideal amount and that they would not just give that information away to someone who could be trying to poach their recipe. I thanked them for their answer and said I as estimating it to be 35 % . They wrote back gob smacked wanting to know how I knew. It would be funny if it wasn’t so sad. Yet another example of a company that appeared to have no clue what they are doing.
