Date: 10/02/2020

When choosing pet food, most pet owners have one focus in mind: protein.

And actually, it could not be otherwise. Balanced protein intake is an essential part of maintaining animal health and quality of life.

Present in all living organisms, it is possible to list a huge variety of functions in which this nutrient acts. It is a fundamental part of tissue formation, as it participates in the regulation of metabolism through hormones and enzymes that perform specific functions in the body.

In addition, it is also part of gene expression, nutrient transport and defense mechanism. Because of this fundamental importance, one can already imagine that choosing the protein source that will be part of pet food is not an easy task.

But to have the knowledge to make a safe choice of protein source, one must first understand what requirements a protein must meet to be considered suitable for pet food.

Protein quality parameters: the five key factors

The ideal amount of protein varies according to the species and age of the animal. For example, according to the American Feed Control Official, adult dog food should contain at least 18% protein on dry basis for body maintenance and at least 22.5% for minimal growth and reproduction at all stages of life.

Regardless of the particularities surrounding the nutritional requirements of each species, the parameters that define the quality of a protein are the same for all of them.

The first of them is the amino acid composition. There must be a balance that takes into account the optimal ratio of essential amino acids. For dogs and cats, for example, they consist of arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.

All of them must be acquired through diet, as they are not synthesized by the organism of these species. However, it is not enough that they are present, because amino acids also need to be available to be properly absorbed and used for basic functions.

It is also necessary that the protein has a high apparent digestibility coefficient, defined as the difference between the amount of protein offered in the diet and the amount excreted in feces. Basically, what the animal’s body will actually use from the protein it has ingested.

The presence of anti-nutritional factors is also a parameter to evaluate, especially when the protein source is of vegetable origin. These substances, when present, reduce the nutritional value of the ingredient as they make it difficult for nutrients to be absorbed.

Finally, the protein source must have good palatability, which can be measured by the amount of feed ingested by the animal. The food needs to be attractive so that pets have the initial incentive to eat them.

But what kinds of ingredients can be used as a protein source?

A very common source due to its high quality is animal protein. It usually comes from poultry, fish, lamb and cattle slaughter co-products. Of the total poultry slaughter volume, 25% is destined to pet food production.

Several ingredients can origin from this type of source, such as chicken protein hydrolysate, for example. It contains all the essential amino acids for dogs and cats, which are in balanced and highly available amounts.

Digestibility is increased due to enzymatic hydrolysis that also generates bioactive peptides, responsible for helping to maintain other aspects of animal health due to their antioxidant action.

Being an animal product, CPH has high palatability as well. Another positive aspect is the absence of anti-nutritional factors.

Far beyond the amino acid profile, animal proteins also have the advantage of being sources of fat and minerals, especially calcium and phosphorus. Plant sources can also be used for pet food production. Among them, one of the most common ones is soy, used in the form of bran.

Soy, however, has some antinutritional factors such as lecithin, phytate and trypsin inhibitors. Therefore, for pet food use, this type of ingredient first needs to undergo heat treatment for inactivation of such substances.

Another disadvantage of soybean is the increased incidence of flatulence and changes in animal feces due to the presence of oligosaccharides.

There is also the possibility of supplementation with synthetic amino acids for cases that a source that does not contain the optimal balance is chosen.

This type of strategy, however, is not unanimous, as some studies point to a lower bioavailability when amino acids are in the free form, so it is preferable that they are consumed in their natural forms (in the structure of proteins) for better use by the body.


There are many variables involved in choosing the protein source that will be part of pet nutrition. Consideration must be given to the particularities of each species and age group in order to understand the needs related to amino acids and other aspects that determine the quality of a protein.

The right choice leads to the development of very nutritionally rich products that can help grow and maintain animal health in a way that would not be possible without proper nutrition.