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Dietary Protein - The Importance Of Digestibility

Want to read a simplified version of this blog post? Check out our corresponding infograph here!

Protein is such an important part of our pets' diets. However, it is also important to understand why our pets need dietary protein and how it affects their health and wellbeing. Remember that pet food packaging may not always provide us with all the information that we need!

Why Protein?

Dogs and cats need dietary protein for the following reasons:

  • Dogs and cats need a combination of 22 amino acids to be healthy. Dogs can synthesize 12 of these amino acids themselves, and cats can synthesize 11 of them. The remaining amino acids must come from the food they eat. This is why they are called essential amino acids.

  • Animal protein provides the essential amino acids that dogs and cats cannot synthesize. Dogs and cats require these essential amino acids in sufficient quantities to remain healthy.

  • Protein also provides dispensable amino acids. These are amino acids that dogs and cats can synthesize, but only if the appropriate nitrogen and carbon sources are provided. Where do these sources come from? Animal protein.

While protein is very important to our pets' health and wellbeing, not all proteins are created equal. Poor quality protein can be harder for dogs and cats to digest and can lead to further complications and health issues. The less digestible the protein, the less essential amino acids gained from their food. Therefore, we should feed our pets good quality digestible forms of protein so that they can derive the essential amino acids from the protein they require to remain healthy.

What Is Digestible Protein?

The digestibility of a protein is determined by the bioavailability of amino acids in our pets' food. All proteins have a biologic value measured in percentage terms, which tells us the usable amino acid content of the protein. The higher the biologic value the better.

For example, eggs have the highest biologic value of all dietary protein at 100%, so they are fully digestable.

Fish and fishmeal are close behind, with a biologic value of 92%. It is important to know that all fresh meat and fish will have a high biologic value compared to processed meat.

Many pet foods contain words on the ingredients list such as “meat and animal derivatives” and “animal by-product”. These terms are legally defined by European Law and a pet food that states that it contains “meat and animal derivatives”, or, “animal by-products may include feathers, beaks, hooves and wool, along with several other animal-based ingredients. While these ingredients are all 100% protein, they have a low usable amino acid content as they are made up of different proteins compared to muscle meat, therefore having a lower biologic value.

The Pros & Cons Of Animal By-Products

Some pet food manufacturers point out that meat and animal derivatives and by-products can be nutritious, and provide dogs and caats with the essential amino acids they require. There are also scientific studies that support this claim.

A significant proportion of scientific studies on the use of by-product in pet food, however, conclude that the digestibility of by-product depends upon the quality of the by-product being used, and on the temperatures that the by-product is heated to during its processing. Studies have also demonstrated that when raw (as opposed to pre-cooked) animal by-products are incorporated into pet food, they have a higher amino acid digestibility.

However, a majority of animal by-products in dry pet food are heated or rendered before being added as an ingredient. As a result, the meat goes through two cooking processes, arguably reducing the amino acid content of the meat even more.

The key issue surrounding animal by-products is that if the manufacturer does not tell us what ingredients make up the by-product, or the process in which the food is manufactured, then we have no way of knowing what is in our pet’s food and whether it contains quality protein.

What To Look Out For

When choosing food, it best to ensure that we select food that contains digestible proteins. Look for foods that contain fresh or dried meat or fish, ideally sourced from lean muscle meat and identified organs such as heart.

Ideally, avoid lower-quality ingredients such as animal by-products, or meat and animal derivatives. Not only will there be limited digestibility of amino acids from this type of pet food, but the indigestible protein may also cause metabolic stress to dog or cats' digestion as their metabolism has to work harder.

Remember, the pet food label does not necessarily provide any measurement of the digestibility of the protein it contains. It’s not enough to check for the protein level on the pet food label, as it is the quality of protein that is used in the pet food that matters. Instead, check the ingredients list to ensure that the food only contains good quality and identifiable sources of animal protein.

Want to read a simplified version of this blog post? Check out our corresponding infograph here!

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