Protein is an essential nutrient for cats and dogs and has several functions in the body including being a structural component of body tissues and organs such as cartilage, muscle fibres, skin and hair, and being critical to components of blood, cells in the immune system and hormones in the body.
A cat or a dog’s dietary need for protein depends upon factors such as their, age or life stage (e.g. growing animal or an adult), physiological state (e.g. pregnancy, lactation or a specific health condition) and how much food they consume in a day.
As a general rule, cats and kittens need more protein in their food than dogs and most other domestic species. They also have a specific need for certain amino acids, for example taurine (an amino acid derivative). The amount of protein and the type selected may therefore differ between prepared cat and dog foods to account for these species differences, and as such, dog food should never be fed to cats as they are likely to miss out on specific key essential nutrients.
Proteins are large molecules containing hundreds, or in some cases, thousands of smaller units called amino acids – think of a protein as a necklace of beads where each individual bead is an amino acid. There are around 20 different types of amino acids that can be strung together to form a huge number of different proteins. The type of amino acids and how they are “strung together” determines the individual properties and function of each protein within the body.
Dogs and cats cannot make all the amino acids they require and must consume enough of certain amino acids in their food. These are called “essential amino acids” and there are 10 essential amino acids for the dog and 11 for the cat. When these essential amino acids are not found in the food in high enough amounts, the cat or dog may develop illness associated with the deficiency.
Protein Quality in Pet Food
The quality of a protein is defined by the individual amino acids that make it up, and how easily it is digested and absorbed by the animal.
Protein can come from both animal and plant-based ingredients. Each type of ingredient will contain different proteins with different arrangements of amino acids. Proteins that contain more of the essential amino acids for cats and dogs that they require in their diet, will be deemed higher quality to include in prepared pet foods. Proteins from animal tissues, such as eggs, fish, poultry and meat are considered good sources of proteins, as they are typically protein rich, and provide a range of essential amino acids.
Protein digestibility refers to how much of the protein eaten is actually able to be absorbed and used by the pet. Animal proteins, such as egg, milk and meat proteins are generally good sources of highly digestible proteins. Proteins are also found in cereals (e.g. corn, wheat and rice) and legumes such as peas or soybeans. These can also be highly digestible sources of protein in prepared pet foods and are used by manufacturers as they are a good source of essential amino acids for cats and dogs.
The dog or cat digests proteins from their food, breaking them up into smaller units (peptides) and their component amino acids, absorbing these into their body. They then use these amino acids to rebuild new complex proteins that are used around the body, wherever they are required.
It should be recognised that growth and reproduction can increase the protein requirements of animals and also the need for certain amino acids. It is therefore often advised to feed foods with elevated protein levels in these cases to ensure the food is meeting the cat or dog’s needs. The changes in protein requirements for pets at different life stages are discussed later in this article.
Understanding the nutritional needs of dogs and cats, selecting appropriate ingredients and producing pet foods with the appropriate protein content for the dog or cat are important considerations for manufacturers of quality prepared pet foods.
What about excess protein? If the food provides enough protein to meet the dog or cat’s needs, providing even more protein does not provide any substantial benefit. Unlike excess fat and carbohydrates, protein is not stored in the body, and excess protein is removed from the body by the kidneys in urine.
When protein is digested and absorbed by the body, the amino acids are used to build new proteins that are required. . These may be proteins for muscle, blood, skin, enzymes used in metabolism, hair growth or any number of other proteins made by the animal. Any excess amino acids that are consumed and absorbed by the dog or cat, that are not converted into these new proteins are not stored to any great extent in the body nor used to make even more muscle tissue. Instead they are processed in the liver to produce energy (calories) that can be used by the dog or cat, and a waste product called urea, which is excreted from the body in the urine.
Protein requirements for different life stages
Pregnant, lactating and growing animals need extra protein in their diet to support these specific life stages. Manufacturers offer a range of prepared pet foods specifically formulated to meet these nutritional needs, often with adjustments to other key nutrients that play a role too.
The extra protein is essential in these different physiological states to help support healthy muscle and brain development in growing animals, foetal growth and development in a pregnant animal and in lactating animals, it helps support the production of milk.
Working dogs who are active for a large portion of the day may also benefit from extra protein in their diet to help maintain their lean muscle mass and repair tissues under strain during work.
Additionally, protein is essential to help repair damaged tissues and replace the protein lost from the body in disease. Extra protein may also be found in diets specifically formulated to help animals recovering from major surgery or severe illnesses – these are often diets that are recommended or prescribed by your veterinarian.
Most healthy, adult pets need only a moderate level of high quality, highly digestible protein for maintenance.
Complete and balanced foods
Fortunately, when you choose to feed quality prepared pet foods, the hard work has all been done. Dogs and cats need a balanced diet which contains the appropriate amounts of protein, fat, carbohydrate, vitamins and minerals to ensure that they stay in peak condition. These nutrients must be present, not only in the correct amounts, but also in regards to some nutrients, the correct proportion to each other to provide a nutritionally complete and balanced diet. Choosing a prepared pet food that includes a statement that the food is complete and balanced for your pet means you’re choosing a food that provides all the nutrition that your pet needs for good health.
This article is for general information only:
This information is provided by the PFIAA as general information only. For advice and information concerning feeding your individual pet, we recommend that you seek the advice of your veterinarian.