Is Your Pet Food Species-Appropriate?

The recipe information you want to enter can be found on the back of your current pet food packaging or on the manufacturer's website.

For cats we used the values published:

• Estimation of the dietary nutrient profile of free-roaming feral cats: possible implications for nutrition of domestic cats British Journal of Nutrition (2011), 106, S35-S48

For dogs we used the values estimated by Steve Brown as published in:

• Unlocking the Canine Ancestral Diet: Healthier Dog Food the ABC Way, Steve Brown

Computing the percentage calories per macro-nutrient is a multiple step process.

First, we compute an approximation of the As Formulated (AF) from the Guaranteed Analysis (GA) values you entered into the form. We assume that the GA values are 10% lower than the AF values, though you can enter a different adjustment by using the "Advanced" table. Note that it is impossible to precisely guess the AF values as the GA values are determined by the manufacturer, typically set at 2 standard deviations from the mean.

Second, we use the Metabolizable Energy equation using the AAFCO required Atwater-modified factors to find the percentage of Nitrogen-Free Extracts (NFEs); NFEs are digestible carbohydrates.

Metabolizable_Energy = 10 * ( 3.5 * AF_Protein + 8.5 * AF_Fat + 3.5 * AF_NFEs)

Carbs = AF_NFEs = ((Metabolizable_Energy/10) - 3.5 * AF_Protein - 8.5 * AF_Fat ) / 3.5

Third, we compute the percentage of calories from each of proteins, fats, and carbohydrates.

percentage calories from proteins = (3.5 * 10 * AF_Protein) / Metabolizable_Energy

percentage calories from fats = (3.5 * 10 * AF_Fat) / Metabolizable_Energy

percentage calories from carbohydrates = (3.5 * 10 * AF_NFEs) / Metabolizable_Energy

The score is a calculated as follows:

Score = 100 - MAX( 100, CF * ( MAX(0, AF_carbs - SA_carbs)) + PF * (ABS(AF_ZC_protein - SA_ZC_protein)) + (FF * AF_Fiber) )

CF: Cats = 2.0 | Dogs = 1.5

FF: Cats = 2.0 | Dogs = 1.5

PF: 0.5

Example for Cats (dogs are the same with different SA values)

	Protein	Fat	Carbs	Fiber
Species Appropriate (SA)	52.0	46.0	2.0	~ 0
SA Zero Carbs (SA_ZC)	53.1	46.9	0.0
As Formulated (AF)	29.9	36.3	33.8	1.4
SA Zero Carbs (AF_ZC)	45.2	54.8	0.0

Score = 100 - min( 100, (2.0 * MAX(0, 33.8 - 2.0)) + (0.5 * ABS(53.1 - 45.2)) + (2.0 * 1.4) )

Score = 100 - min( 100, (2.0 * MAX(0, 31.8)) + (0.5 * ABS(7.9)) + (2.0 * 1.4) )

Score = 100 - min( 100, (2.0 * 31.8) + (0.5 * 7.9) + (2.0 * 1.4) )

Score = 100 - min( 100, 70.3 )

Score = 100 - 70.3

Score = 29.7

Rationale

CF – Cats are strict carnivores so we penalize excess carbs heavily with a 2x factor, while dogs are facultative carnivores so we only penalize excess carbs with a 1.5x factor.

FF – Fiber isn't a part of AAFCO's metabolizable energy calculations. Penalize fiber with the same penalities as for Carbs.

PF – USDA proteins have different ratios of amino acids and fatty acids making it difficult to impossible to meet the AAFCO nutrition profiles without adding carbs or becoming unbalanced in the protein/fat ratio. As a result we only count half the protein deviation in our scoring.

The difference between the AAFCO and Premium Pet Food calculation is the scale factors used to convert grams of a macro-nutrient into metabolizable energy. The amount of energy changes depending on the specific nutrient source making it difficult to have a universal set of scaling factors.

• AAFCO chose a set of parameters called Atwater Modified for use on their standard guaranteed analysis information to make it easy for consumers to compare different products. This set of parameters is a reasonable compromise for processed foods and ingredients.
• However, research and practical experience are showing that premium foods using minimally-processed ingredients may be better represented by the original Atwater factors. In our advanced tab we default to calculating the as formulated metabilizable energy using the Atwater factors.