On my Facebook page, K9Nutrition, protein content in a dog’s diet is a popular topic. Debates occur on the value of various proteins such as beef, pork, venison, eggs, turkey, chicken and more.
Sometimes the discussion veers to the value of carbohydrates. Like animal-based foods, carbohydrates can also contain proteins.
However, they are mostly non-essential amino acids, these can be made by the body and it not necessary to eat foods containing these.
But essential amino acids must be consumed by carnivores, and these are found in animal sourced foods.
There are a few plant based food that contain essential amino acids, but the amounts dogs would need to consume make this not reliable in amount or balance.
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I have more about this in my article on the harm of feeding a dog a vegan or vegetarian diet.
Keep in mind, both animal-based products have amino acids as do plant based foods.
But dogs, as carnivores need the essential amino acids found in abundance in animal-based foods that are missing from plant -based foods. Now we will explore the methods of how to determine the amount of protein.
AAFCO uses Crude Protein to determine the percentage of protein in dog food.
A measure of the amount of protein in a feed determined as the amount of nitrogen multiplied by 6.25. The factor 6.25 is the average grams of protein that contains 1 gram of nitrogen.
The word “crude” refers to the fact that not all nitrogen in most feed is exclusively in the form of protein. Because most feeds contain non-protein nitrogen (NPN), crude protein generally overestimates the actual protein content of a feed. (Protein Determination—Method Matters)
Measuring protein by nitrogen content is highly inaccurate.
Some plants contain nitrates which also causes the protein levels to appear higher than they contain. Plant based foods that are high in nitrogen include:
- Tofu and soy-based products.
- Beans, including lentils, garbanzo, black, pinto and kidney beans.
- Nuts such as almonds, hazelnuts and walnuts
- Seeds, including sesame seeds
- Peanut butter
- Nitrate-rich vegetables include leafy greens like spinach, lettuce and beetroot.
- celery, parsley, leeks, fennel and endive, spinach
- Bok Choy. Out of the cabbage family, bok choy is the highest in nitrates.
- Carrots.
Please note, soy (tofu) and spinach block the uptake of calcium in dogs, so I never recommend feeding either to dogs.
Dog foods containing the above carbohydrates may show higher amounts of protein that it really contains. (What Foods Are High in Nitrogen?)
“If it’s not actual usable protein that is listed under the crude protein section of pet food, then what is it? Protein is primarily determined by nitrogen content, but the crude protein in pet food may include nitrogen that isn’t actually protein – often that nitrogen is not from animal tissues and is referred to as “non-protein nitrogen.””
While non-protein nitrogen can be incorporated from either natural or unnatural sources, the common source of non-protein nitrogen in pet foods is from plant ingredients.
And unfortunately, some dog food companies have been guilty of ‘doping’ dog food by adding nonfood nitrogen substances.
In 2007 melamine was added to pet food to raise the nitrogen count, which in turn artificially raised the protein count.
Sadly, this caused kidney failure and the death of many dogs. (The “protein illusion”: nitrogen doping in pet food)
For instance, in a recent review by Angell et al. [4] it was shown that 52% of all studies on the protein content of seaweeds used nitrogen determination with subsequent conversion using a nitrogen-to-protein conversion factor of 6.25. This is in spite of many studies documenting that this factor leads to an overestimation of the protein content in most foods and, in particular, plant foods [5,6,7].
The results from this study show that protein determination based on nitrogen analysis for most food matrices overestimates the protein content compared to amino acid analysis, whether or not the species-specific conversion factors are used.
Protein Determination—Method Matters
The importance and bioavailability of protein in human nutrition has been emphasized.
- Amino acid count is a better determinant for total protein content.
- In the study, complete amino acid profile of beef amounted to 91% of protein based on total Nitrogen.
- Results are in line with results showing that the Jones factor might overestimate protein content.
Total nitrogen vs. amino-acid profile as indicator of protein content of beef
The best way to determine protein content in food is:
- The Protein Digestibility-Corrected Amino Acid Score (PDCAAS)
- The more recently developed Digestible Indispensable Amino Acid Score (DIAAS)1
Total nitrogen vs. amino-acid profile as indicator of protein content of beef
This is used by dairy farmers and most other human based foods.
But it has not been adopted by the pet food industry. Part of the reason may be a higher cost to determine an accurate protein count and changing their old method could be costly.
I can only speculate that another reason may be that their protein counts would show lower numbers and could not be raised by increasing nitrogen in the dog foods.
Whatever the answer might be, the process to change determination of protein in dog food needs to be changed immediately.
There are numerous medical reasons, along with other health concerns, not to mention having accuracy in labeling of pet foods. I might suggest we all write pet foods companies and request this. Usually pet food companies will listen to consumer concerns.
Of course, the safest way to know what your dog is eating, is to feed fresh food.
Either making your own, home cooking or buying frozen premade raw. Bone appetit and stay healthy!
