Comparing Apples to Apples
Most state regulations require a pet food manufacturer to guarantee the minimum percentages of crude protein and crude fat, and the maximum percentages of crude fiber and moisture, and to clearly display those guaranteed analyses on the product labelling. Those percentages often become an important basis for consumers to compare products. However, those percentages can be misleading when comparing foods with vastly different moisture contents.
As noted by the FDA, meaningful guaranteed analysis comparisons can only be made when foods are evaluated on the same moisture basis, known as the dry matter basis. That is an important point to remember, as illustrated by the simple example that follows.
In order to undertake a dry matter basis comparison of foods, we must first remove the moisture content from the foods being compared. We do that by subtracting the percentage moisture content of each food from 100%. That calculation reveals that a kibble with 10% moisture is composed of 90% dry matter, while a raw food with 70% moisture is composed of 30% dry matter. We can now use those two dry matter percentages to do a meaningful comparison of the protein, fat, and fiber levels in the two foods.
The label on the kibble indicates a protein percentage of 38%. We divide that percentage by the percentage of dry matter we calculated to be in the kibble (90%), and find that the kibble contains 42% protein on a dry matter basis. Here’s the math: 38 ÷ 90 = 0.42 or 42%
The label on the raw food indicates a protein percentage of 16%. We divide that percentage by the percentage of dry matter we calculated to be in the raw food (30%), and find that the raw food contains 53% protein on a dry matter basis. Here’s the math: 16 ÷ 30 = 0.53 or 53%
Similar calculations can then be made to reveal the fat and fiber percentages of each food on a dry matter basis. Here’s what all those numbers reveal:
Kibble with moisture dry matter basis
Protein 38% 42%
Fat 18% 20%
Fiber 5% 5%
Moisture 10% 0%
Raw Food with moisture dry matter basis
Protein 16% 53%
Fat 10% 33%
Fiber 2% 6%
Moisture 0% 0%
Cheers to you and your pets!