Visit any Internet message board about pet nutrition and you will more than likely find a heated debate about protein — pros, cons, good sources, bad sources and more opinions than you ever wanted to know. What is protein and why is it such a hot topic?
What is protein?
Proteins are the building blocks of your pet's body and consist of chains of amino acids joined together. They can range in size from only a few amino acids to large, complex molecules in which the amino acid chains are intricately folded.
Both the sequence of the amino acids as well as the three-dimensional structure affect the protein’s function. Proteins are necessary for all aspects of growth, development, body tissue repair, digestive enzymes and the immune system. Among the three energy-providing macronutrients — protein, fats and carbohydrates — protein is unique because it is the body’s primary source of nitrogen.
There are 22 amino acids that dogs and cats require, but they can only make 12 of these (i.e. nonessential amino acids). The remaining 10 are essential amino acids that your pet must get from food (see table). Cats are unique because they also require taurine, an amino acid-like compound.
Taurine is only found in animal protein sources, so it is important for cats to get at least some of their protein from meat. Taurine is critical for a cat's normal heart, eye, and reproductive function. Complete and balanced pet foods must contain all of the essential amino acids in amounts that meet the requirements for cats or dogs.
Dietary protein sources
Good sources of protein commonly used in pet foods fall into three main categories: meals (e.g., chicken meal, lamb meal), fresh meat/fish/poultry (e.g., de-boned turkey, de-boned venison) and plant-based protein (e.g., pea protein, corn gluten meal).
When foods containing protein are eaten, this dietary protein is broken down into amino acids, which are then absorbed and used to make body proteins. However, not all proteins are created equal.
A highly-digestible protein source that contains greater amounts of essential amino acids is considered a high-quality protein. Some proteins contain low levels of one or more essential amino acids, referred to as the limiting amino acid, usually methionine, lysine or tryptophan. However, foods can easily be combined to provide the correct balance of all essential amino acids (i.e., complementary proteins).
Protein requirements
Protein levels in pet foods have been slowly creeping up over the years, but how much do dogs and cats really need?
Protein requirements vary depending on species and life stage. Cats are obligate carnivores and need more protein than dogs. Puppies and kittens have higher requirements than adult dogs and cats because the additional protein is necessary for new tissue development.
According to the Association of American Feed Control Officials (AAFCO), adult dogs and cats require a minimum of 18 and 26 percent protein (dry matter basis), respectively, while ensuring that all essential amino acid requirements are met. Higher protein levels may be needed in some circumstances, such as high performance animals or critically ill patients.
Conversely, decreased protein levels may be necessary for some health conditions. One factor to consider with very high-protein diets is that other nutrients may get out of balance. For example, diets very high in meat may not contain the proper calcium to phosphorus ratio, which can impact bone and kidney health. Properly formulated pet foods contain a balance of protein, fats and carbohydrates, as well as vitamins and minerals.
Protein and health issues
Fats and carbohydrates are the preferred energy sources for the body, but protein can also be broken down to provide energy. However, animals are unable to store an excess of amino acids. What is not utilized for tissue maintenance has to be dealt with by the liver and kidneys. Obesity is a major concern for an increasing number of pets. For pets that need to lose a pound or two, evidence suggests that a higher protein diet may be beneficial. While energy balance ) is the key factor in weight management, a moderate protein boost may help to encourage the loss of body fat while preventing the loss of muscle tissue for pets on a calorie-restricted diet.
Protein is the component in food that is the most common source of food allergies. Novel protein ingredients that your pet has not eaten before are less likely to cause an adverse food reaction. Some examples of novel proteins include venison, salmon and duck. If you suspect that your pet may have a food sensitivity, more information can be found here.
In the past, it was widely accepted that pets with kidney impairment should eat a low protein diet. The kidney plays an important role in regulating the amount of nitrogen in the blood. High blood nitrogen levels, called azotemia, results in side effects such as confusion, rapid heart rate and excessive thirst. Since protein is the primary dietary source of nitrogen, it was believed that restricting protein intake would reduce azotemia and protect the kidneys from additional damage.
Although dietary protein intake may need to be adjusted depending on the clinical condition and symptoms of the pet, extreme protein restriction is no longer advised for most pets with kidney failure. In fact, getting enough high-quality protein is vital to maintaining health and preventing malnutrition for animals with chronic renal failure.
Protein is a vital component in your pet’s food and provides the essential amino acids your pet needs to be strong and healthy. However, it is important to remember that like most nutrients, while some is good, a lot is not necessarily better.
