Kangaroo meat (dog treats) Protein value is in its digestibility & bioavailability

On May 21, 2014 by Big_Grey

grey kangaroo 5For a long time I have been struggling to come to terms with why kangaroo dog treats are so amazingly healthy for dogs. The high quality fats have a lot to do with it, but I wanted to know more about what makes the proteins so good. Proteins are vital to a dog’s health and meat proteins have been known to be the best for dogs for a long time. They need protein for basic body functioning and for growth and repair of body and tissue. So why are kangaroo proteins so good?

Proteins are made up of amino acids, and ten of the amino acids (relatively short chain molecules) are called essential amino acids because they can’t be easily manufactured within the dog for nutritional use. For example insulin is a protein made up of 51 amino acids joined in a specific sequence.

The AAFCO (dog food manufacturer minimum nutrient requirements) state minimum requirements for the ten amino acids, but not the source. Contrary to some views, extra protein will be easily broken down and excreted as a normal function of the kidneys

The issue for many dog’s health is that most dog food you can buy is full of grains to make up cheap calories. Because many grains are not as easy for dogs to digest (break down the protein into amino acids for the dogs body to use), they often need a diet higher in protein as a percentage of total calories.

Protein digestibility and protein bioavailability. 

These are two of the most important factors in what is classed as high quality protein.

Protein digestibility means how much of the amino acids of dog food can be broken down by the digestive system. Protein digestibility varies between species (i.e. human and dog) as well as between breeds of dogs.

The next issue is considering what quality protein is called the bioavailability. The term bioavailability means the relative amount of ESSENTIAL amino acids in a food compared to the total protein content. There is not a lot of value in feeding your dog a protein source that has mostly non essential amino acids in it. Their body can already make and use non essential proteins itself, Essential proteins are the real issue.

If you feed your dog a proteins source that is high in essential amino acids, you will not have to feed them as much, meaning you are less likely to over feed your dog (excess calories) to achieve the minimum level of essential amino acids required.

Unfortunately bioavailability has mostly been studied for humans (who are omnivores, and not carnivores like dogs). There is likely to be similarities but the aim of feeding your dog is to have a protein source that is highly digestible AND highly bio-available!

Protein Digestibility Corrected Amino Acid Score (PDCAAS)

A few decades back nutritionists wanted to create an all encompassing scale that would enable you to classify the value of each protein source, regarding digestibility and bio-availability, and they came up with the Protein Digestibility Corrected Amino Acid Score (PDCAAS)

” The method is based on comparison of the concentration of the first limiting essential amino acid in the test protein with the concentration of that amino acid in a reference (scoring) pattern. This scoring pattern is derived from the essential amino acid requirements of the preschool-age child. The chemical score obtained in this way is corrected for true faecal digestibility of the test protein. PDCAAS values higher than 100% are not accepted as such but are truncated to 100%.” ref 3

You may wonder why I am telling you this when what we are talking about is dogs and dog treats digestibility. Well in the absence of any rigorous testing with the specific dog species, this is what information we have to work with at the moment, and again, many sources believe the results would be similar.

There are many papers discussing the limitations and variability of the results of this PDCAAS scale, however as it is the most widely accepted and most widely used scale it is worth talking about here.

The Following reference pattern of amino acid concentrations in a test group of school children. It “was obtained by computing the ratios between the essential amino acid requirement values (mg/kg body weight/d) and this safe level of high quality protein intake (g/kg body weight/d), thus resulting in values of mg/g of protein for each essential amino acid.” ref 2

FAO/WHO/UNU amino acid requirement pattern based on amino acid requirements of preschool-age child1

Amino acid Requirement
mg/g crude protein
Isoleucine 28
Leucine 66
Lysine 58
Total sulfur amino acids 25
Total aromatic amino acids 63
Threonine 34
Tryptophan 11
Valine 35
Total 320

(From FAO/WHO/UNU Expert Consultation 1985).

True faecal digestibility, amino acid score and PDCAAS for selected proteins ref 3

Protein PER Digestibility AAS PDCAAS
Egg 3.8 98 121 118
Cow’s milk 3.1 95 127 121
Beef 2.9 98 94 92
Soy 2.1 95 96 91
Wheat 1.5 91 47 42

( Data from FAO/WHO Expert Consultation 1990, European Dairy Association 1997, and Renner 1983).

Concerns about the Truncation of PDCAAS values to 100%

As you can see from the above table, the chicken egg is undoubtedly a great protein source for humans (and dogs) however dogs should only eat cooked egg, and only 2-3 per week whole eggs (more science articles recently showed this).

While cow’s milk is shown to have a high PDCAAS score the sugar lactose is usually poorly digested by most people and dogs. Hence why lactose free milk for dogs was created.

Beef is the only meat source shown in the article and as you can see it is near the 100 value that most proteins aspire to. Considering that kangaroo meat is considered to be a better protein source again, you would expect (if it was tested) to have a similar if not greater score.

What you should also focus on is that Wheat has a PDCAAS of 42. This explains why it and other grains that are readily used in commercial dog food are not easily digested, so any nutrition they might supply is drastically reduced.

The original theory for truncating protein values to100% was because ” digestible essential amino acid concentrations in a protein in excess of those in the preschool-age child reference pattern do not provide additional nutritional benefit. ”

However, subsequently scientists agreed that the major flaw in this logic is that “the statement is correct when the protein in question is the sole source of protein in the human diet, as occurs in infant feeding practices and under special conditions, like enteral feeding. However, under all other conditions, humans consume mixed diets with proteins from a variety of sources. ” ref 2

“Under such conditions, the power of high quality proteins to balance the amino acid pattern of the mixed diet is extremely relevant. A classic and widely accepted example in this regard is the combination of milk and wheat, in which the relatively high lysine concentration of milk proteins compensates for the low concentration of this essential amino acid in wheat. So it can easily be computed that 1.2 g of casein can balance 1 g of wheat protein, whereas 6.2 g of soy protein would be needed to do so.” See below:

Amount of protein needed to upgrade 1 g of wheat protein to obtain the preschool-age child’s lysine requirement level of 58 mg/g mixed crude protein

Protein Protein supplement needed
Beef 1.0
Cow’s milk 1.6
Egg 2.6
Soy 6.2

” The truncation of PDCAAS values thus largely eliminates the differences in the power of high quality proteins to balance the amino acid composition of inferior proteins. This is highly relevant, not only for the low lysine content of cereals but also for the low content of S-containing amino acids and threonine of many plant protein sources. Thus, truncated PDCAAS values do not provide information about the potency of a protein to balance inferior proteins, and a solution for this problem should be found. ”

This last paragraph is extremely relevant to many dog foods that are grain based (what or rice etc).

Not only can kangaroo meat provide excellent quality protein that is readily digestible and bio available to your dog via kangaroo dog treats, but it is likely that these can compensate (even with kangaroo is used in small quantities like in kangaroo dog treats) for any low value of essential amino acid in the base grain used in the commercial dog food.

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