Nutrient requirements

The nutrient requirements of dogs and cats is a hot topic in the pet food industry at the moment. Manufacturers are selling “high-protein” diets, foods with added fatty acids, or diets supplemented with other attractive ingredients. Much of these are marketing tactics used by pet food companies to appeal to pet parents. Researchers have been studying dog and cat nutrient requirements for decades, so their needs are very well-understood, and there are many regulations for pet food companies to follow to ensure pets get what they need.

Unfortunately, it is nearly impossible for pet owners to determine if a food meets certain nutrient requirements simply based on the label. Therefore, we must rely on the manufacturer’s compliance with rules and regulations set by AAFCO and the FDA. To ensure your pet is getting all the nutrients they require from their food, visit How to pick a pet food, part 1.

Though pets’ nutrition requirements are difficult to understand, it is good for pet owners to recognize each nutrient in a pet’s diet and understand why it is there. Read on to learn more!

Nutrients v. ingredients

Nutrients are essential components of the diet that are necessary for life. Nutrients include things like water, energy, protein, fat, carbohydrates, vitamins, and minerals.

Ingredients are the sources of nutrients. A single ingredient can provide many different nutrients in different proportions. The name of an ingredient itself tells you nothing about the quality of nutrition it provides.


Water is the most important nutrient. Pets should always have access to free choice water throughout the day. Water should be clean and room temperature. Tap water is fine for our dogs and cats to drink, as long as it is safe for human consumption. However, hard water should not be given to pets with urinary problems. You may provide pets with bottled or filtered water at your preference. 

Requirement: At the very least, our dogs and cats require the same number of milliliters (mL) as their required kilocalories (kcal) each day (see How to calculate your pet’s calorie needs to learn more). This requirement increases with physical activity, illness, increased ambient temperature, and many other factors, so it’s best to simply allow your pet to have as much water as they like to prevent dehydration.


Energy is the second most important nutrient. Energy is provided in the diet by protein, fat, and carbohydrates. Energy is expressed in kilocalories (common in small animal nutrition), or Calories (common in human nutrition), but these terms mean the same thing.

[Flowchart adapted from Small Animal Clinical Nutrition.]

Feeding the right amount of a balanced commercial pet food that meets your pet’s energy requirements will ensure they will receive the necessary amount of all other nutrients. To learn more about complete and balanced pet food, visit How to read a pet food label.

Requirement: Every pet has different kilocalorie requirements. You can use the recommendations on the pet food label, but you will have to adjust to get the right amount, or you can use a scientific calculation (see How to calculate your pet’s calorie needs to learn how).

When pets are fed too much energy, they store the nutrients they don’t need as fat, thus gaining weight. It is very important to feed your pet the appropriate amount of kilocalories to prevent obesity. See How to body condition score for more information about obesity.


Protein is in the diet to provide your pet with energy and amino acids. 

Requirements: The percentage of protein in a diet will vary based on the number of kcals per gram of food; therefore, the percentage of crude protein on the guaranteed analysis will not tell you if the protein requirement is met. At a minimum, healthy adult dogs require 18% protein on a dry matter basis (DM). Healthy adult cats require at least 25% protein by DM. Puppies, kittens, and pregnant or lactating mothers require more protein in their diets than adult animals.

Amino acids

Amino acids are the building blocks of proteins. There are 22 different amino acids, which are broken up into essential and non-essential groups. Essential means the animal cannot make it on their own and it needs to be in their diet. Non-essential means the animal can make it on their own, so it doesn’t need to be in their diet.

Requirements: Essential amino acid requirements are different for growing versus adult animals, and also differ between dogs versus cats – a major reason why buying a life stage and species–labeled diet is critical (see How to pick a pet food, part 2 for more information). Dogs and cats both require the amino acids arginine, histidine, isoleucine, leucine, methionine, phenylalanine, tryptophan, threonine, and valine. Cats also require taurine, which is found only in animal proteins (one of the reasons cats are described as “obligate carnivores”).

Protein quality

For most consumers, a common estimation of quality is represented by clean, wholesome ingredients like boneless, skinless chicken breast. However, the nutritional definition of quality is much more than that. A high-quality protein source is one that is highly digestible and that contains many essential amino acids. Here are a few ways protein quality can be assessed:

Here are some examples of common ingredient sources of protein, and how they compare to one another:

[Table adapted from Nutrition and Disease Management for Veterinary Technicians and Nurses, second edition.]


Fat is in the diet to provide pets with a source of concentrated energy, because fat has more energy per gram than protein or carbohydrates. Fat also enhances the diet’s palatability (i.e., how good it tastes to your pet). Fat provides your pet with essential fatty acids, and it also helps pets absorb fat-soluble vitamins found in the diet.

Digestibility of fat varies based on the ingredient providing that fat. (For example, coconut oil is very poorly digested by dogs and cats. It also does not contain any of their essential fatty acids.) On average in commercial pet foods, average fat digestibility ranges from 75-90%, so it is a very digestible nutrient.

Requirement: Healthy adult dogs and cats do not technically have a minimum fat requirement, but fat is required to provide the essential fatty acids (see below). Growing puppies and kittens as well as pregnant/lactating mothers require more energy than adult animals, and can therefore benefit from a diet higher in fat.

There is no maximum fat content for pet foods, but the higher the fat . . .

Fatty acids

Fatty acids are the building blocks of fat.

Requirements: Adult dogs and cats require alpha-linolenic acid (one of the Omega-3s) and linoleic acid (an Omega-6). Adult cats also require arachidonic acid (Omega-6), which is found only in animal fats; another reason they are “obligate carnivores.” Growing, pregnant, and lactating animals also require eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the other two Omega-3 fatty acids.


Carbohydrates are the diet to provide your pet with energy. Ingredients that provide carbohydrates cost less than sources of the other energy-containing nutrients, protein and fat. This prevents fat and protein being used for energy, so those nutrients can be used to fill amino acid and fatty acid requirements, rather than energy requirements. Carbohydrate sources can also provide other essential nutrients, depending on the ingredient source. Additionally, they provide a source of fiber to the diet.

Dogs and cats can in fact digest and utilize ingredients that supply carbohydrates (see Grains as “fillers” for more info). Cooking of carbohydrate sources also greatly increases their digestibility. Digestibility of carbs in commercial pet foods ranges from 73-94%, so they can be highly digestible.

Requirement: Technically, adult dogs and cats do not have a requirement for carbohydrates; the body can make glucose (AKA sugar) for energy from other sources, like protein and fat. However, pregnant and lactating dogs do have a carbohydrate requirement (23% of DM), as glucose is utilized as a primary energy source by their developing and growing offspring. 


Fiber comes from carbohydrates that are not easily digested for energy. Fiber is mainly used to alter and maintain bowel function and stool quality. Fiber is also used to reduce energy density of a food (i.e., how much energy is in a given volume), specifically in weight-loss diets. There are many different types of fiber, all of which affect the digestive tract differently. On average, pet foods contain 2-4x as much fiber as human diets!

Fiber alters the way other nutrients (energy, fat, protein, carbohydrates, and minerals) are absorbed. Therefore, if a diet which has not been prepared or tested correctly contains too much fiber, pets can develop other nutrient deficiencies. To avoid this problem, stick with a reliable and high-quality commercial diet (see How to pick a pet food, part 1).

Requirement: No true fiber requirement has been established, and ranges between pet foods vary. However, diets without any fiber do not produce normal stool, and diets with too much fiber are not easily digestible and can cause constipation. A fiber level of 5% or less is recommended for healthy animals.


Vitamins are in the diet because they contribute to many cellular processes in your pet’s body. They do not provide energy, but they do regulate how energy is used by the body (also known as metabolism).

Types of vitamins include the fat-soluble vitamins (A, D, E, and K), and the water-soluble vitamins (B-complex and C). Vitamins are found in natural sources, such as ingredients that supply other nutrients. However, the cooking process can destroy or weaken vitamins, so manufacturers may add synthetic vitamins in after the diet has been cooked.

Requirements: Dogs and cats require different vitamins in very precise amounts. The fat soluble vitamins are required in the diet of dogs and cats. Excesses of these vitamins can be life-threatening, and therefore these vitamins should not be supplemented if your pet is eating a complete and balanced commercial diet (see Supplements for more details). Several water soluble vitamins are required in the diets of dogs and cats, including thiamine (vitamin B1), riboflavin (B2), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folate (B9), and cobalamin (B12). Cats also require niacin (B3).


Minerals are in the diet because, like vitamins, they contribute to many cellular processes in the body. Even though they do not provide energy, they are very important for things like bone strength and red blood cell function.

Requirements: Minerals compose a very small part of the diet, and each mineral is required in different amounts. Macrominerals such as calcium, phosphorus, potassium, sodium, and magnesium are needed in greater amounts. The balance of certain macrominerals like calcium and phosphorus is crucial; imbalance can lead to bone disease and other metabolic problems. Microminerals like iron, zinc, copper, manganese, iodine, and selenium are needed in tiny quantities. Deficiency or excess of any mineral is very serious and can have life-threatening consequences, especially in growing animals, so it is important that you do not supplement minerals if your pet is eating a complete and balanced commercial pet food (see Supplements for more information).