Energy

What is Energy?

Energy is a term that can have different meanings depending on the context. In the context of dog behavior, energy is often used to describe a dog’s activity level as either high or low. While nutrition can play a role in a dog’s behavioral energy, the relationship between the two is not straightforward. Factors such as age, activity level, breed/type, and personality can all influence a dog’s energy level. It is important to recognize that nutrition provides the energy necessary for survival and daily activities. Feeding a high-energy diet does not necessarily result in a more active dog; instead, it may lead to weight gain. For highly active dogs, it is important to provide sufficient fuel for their activity level.

Our dog’s diet must meet their energy needs before other nutritional requirements.

In nutritional terms, energy refers to the amount of fuel provided by a diet. Energy is a critical component of any diet and is derived from nutrients such as fat, protein, and carbohydrates. Balancing these nutrients in a diet can provide the appropriate amount and form of energy for an individual dog’s needs.

All animals require a constant supply of energy for survival. When formulating canine diets, the starting point is determining the daily energy requirements of the dog. Once these requirements are met, other nutrients can be considered. Focusing on ingredients rather than nutrients can be problematic when assessing the suitability or quality of a diet. Instead, considering the nutrients that provide energy can help determine the form and amount of energy provided by a diet and is a better way to assess its suitability.

Where Does Food Energy Come From?

All food energy originates from sunlight. Through photosynthesis, plants convert sunlight into stored energy in the form of carbohydrates such as starch. Animals consume plants and use their energy to support activity and create their own energy stores, primarily in the form of fat. While animals do store some energy as glycogen in muscles and the liver, these stores are small compared to fat stores.

Dogs can obtain dietary energy from carbohydrates, protein, and fat, with fat being the preferred source for their metabolism. Diets consisting of both animal and plant material provide a mix of energy-providing nutrients. This can be useful for managing overall dietary energy intake and tailoring diets for specific purposes.

What Does Energy Mean for Feeding Our Dogs?

The term “energy” can sometimes be misunderstood in the context of dogs. High-energy dogs are often breeds that are naturally active and busy. These dogs may struggle to gain or maintain weight and are often naturally lean but healthy. Low-energy dogs, on the other hand, may be more relaxed and sedentary and may gain weight more easily. In these cases, energy refers more to the dog’s personality and biology than nutrition, although nutrition may need to be adjusted to suit individual needs.

Dog diets are formulated based on energy requirements. A dog’s energy needs are estimated and a diet is created to meet those needs by feeding a specific amount of food. If less food is fed than recommended, other nutrients may not be supplied at the correct levels and deficiencies can occur. This is why feeding guidelines on commercial dog foods are important. Feeding less than the recommended amount can result in nutritional inadequacy. Understanding both a dog’s energy needs and the amount of energy provided by food is important.

Energy originates from sunlight and is converted into stored forms by plants through photosynthesis. This energy is then transferred through the food chain when plants and animals are consumed by other organisms.

Energy Balance

Energy balance is important for ensuring that a dog’s diet provides the energy needed to support daily life processes and activity. In simple terms, to maintain a healthy body weight, energy intake from food should be balanced with energy output from bodily processes and activity. If more energy is consumed than is expended through activity, the excess energy will be stored as fat and the animal will gain weight. Consistent excess energy intake can result in weight gain and obesity, which is the most common form of malnutrition in domestic dogs. Obesity can have a significant impact on a dog’s well-being and lifespan.

Energy balance refers to the equilibrium between the energy consumed from food and the energy expended through the maintenance of bodily processes and physical activity levels.

If an animal’s diet does not provide sufficient energy to support its activity output, it will lose body weight as it uses stored energy sources to meet its energy needs. Prolonged dietary energy deficiency can result in severe weight loss, lethargy, and other significant health and well-being concerns, including deficiencies in other nutrients. Maintaining an appropriate energy balance is a simple way to maintain a healthy body weight.

Energy and Food Intake

An animal’s energy requirements must be met through its diet. While animals are generally adept at balancing their food intake with their energy needs, many factors can impact this balance and result in dysregulation of appropriate food intake. If high-energy diets are readily available and physical activity is limited, as is often the case for many companion dogs, the natural balance between intake and output can become skewed towards excess energy intake and the development of overweight and obesity.

Excessive food intake resulting in an excess provision of energy can lead to obesity. In growing puppies, it can also cause skeletal and other developmental abnormalities such as hip dysplasia, particularly in large breeds. It is also possible that young dogs carrying excess body fat may be predisposed to obesity as adults due to the development of their adipose cells.

On the other hand, if food intake and energy consumption are restricted, this can result in reduced or impaired growth and development in young dogs. In adult dogs, it may impair healing and tissue repair and result in loss of body weight and muscle mass. Dogs with high-energy output, such as pregnant or lactating dogs, highly active or hard-working dogs, may exhibit weight loss if their food intake does not meet their dietary energy requirements.

For dogs that need to gain or lose body weight, it is essential to conduct a diet review and audit to ensure that their energy and other nutrient requirements are met and that an appropriate volume of food intake is provided to satisfy them. A balance must also be struck between the volume of food fed in single meals and the digestive system’s capacity to process and absorb the food. In some cases, this may mean increasing the number of meals per day and feeding a diet that provides more energy in each meal.

How is the Energy in Food Determined?

The energy content of food can be measured in a laboratory using a process called bomb calorimetry, in which the food is burned and the released energy is collected. Food energy is expressed in kilocalories (kcal) or kilojoules (kJ), with 1 kcal equal to 4.184 kJ. A kilocalorie is the amount of energy required to raise the temperature of 1 kg of water by 1°C (from 14.5 to 15.5°C).

In canine nutrition, kilocalories (kcal) are often used to describe the energy content of a diet and/or the energy needs of a dog. While “kilocalorie” is the correct term, it is often shortened to “calorie,” even though technically a kilocalorie is equal to one thousand calories. For clarity, the term “kilocalorie” (kcal) will be used when referring to the energy content of a dog’s food.

How Much Energy is there in Food?

Calorimetry allows us to determine the amount of energy present in food. The total energy released during calorimetry is the food’s gross energy (GE) and represents the maximum potential amount of energy that the food can supply. However, animals cannot utilize all the energy in food due to energy losses during digestion and the processing of food. Digestible energy (DE) is the energy from food that is available after digestion but before urinary and digestive gas energy losses. After accounting for these energy losses, the amount of energy available for the dog’s body to use is called metabolizable energy (ME). ME is used to indicate the energy content of dog food and the amount of energy individual dogs require. ME can be determined through feeding trials or calculated to obtain an estimate of a food’s energy content.

The Energy-Providing Nutrients

Dietary energy is provided by carbohydrates, proteins, and fats. The proportion of each energy-supplying nutrient in a diet varies based on an individual dog’s biology and needs. While each of these three nutrients supplies energy, they differ in how the body digests, absorbs, and processes them. They also differ in the amount of energy they supply, meaning that the energy density (sometimes referred to as calorie or caloric density) of a diet can be altered by changing the amount of each nutrient. Diets that are energy-dense will have a higher inclusion of fat than diets that are energy-dilute because fat supplies more than twice the kilocalories per gram than either protein or carbohydrate. Energy-dense diets are useful for dogs that require a concentrated dietary supply of energy, such as highly active dogs, while energy-dilute diets are more suitable for less active dogs.

How Much Energy Do the Nutrients Provide?

Dogs are metabolically pre-adapted to use fat as a source of energy. Fat supplies an average of 8.5 kcal per gram (kcal/g), compared to protein and carbohydrate, which each supply only 3.5 kcal/g. These values are known as Modified Atwater Factors and take into account the digestibility of the nutrients to provide an estimate of the amount of energy each nutrient provides. For fresh or home-prepared dog foods that are more digestible than commercial diets, Atwater Factors are often used, where fat supplies 9 kcal/g and protein and carbohydrate supply 4 kcal/g. These values can help calculate the amount of energy in food if you know the amount of each energy-providing nutrient it contains.

Calculating the ME Content of a Dog Food

Knowing the metabolizable energy (ME) content of a food is useful for ensuring that you provide enough energy to support your dog’s activity levels. It is also important if your dog requires a weight management program. The energy density of a food also affects its other nutrient content, and the nutrient content of food is often described in units of nutrient per 1,000 kcal ME to facilitate comparisons between different foods.

The ME value of commercial food is sometimes available on the packaging or directly from the manufacturer, making it easy to access this information. However, you may occasionally need to calculate it yourself. To do this, you need to know the percentages of protein, fat, water, fiber, and ash in the food. This information can be obtained from food labels under “analytical constituents” or from reference tables. You also need to calculate the food’s nitrogen-free extract (NFE), which provides an estimate of its non-fiber carbohydrate content.

The following steps and equation can be used to give you an estimation of the ME content of a food:

1. Calculate the NFE content by subtraction:

   %NFE = 100 — %protein — %fat — %fibre — %ash — %moisture

2. Calculate the energy supplied by each of the energy-providing nutrients using Atwater/Modified Atwater factors (depending on digestibility of food).

3. Add the energy provided by each nutrient together to get the total ME of the diet.

Worked Example

Wet dog-food: 70% moisture, 12% protein, 10% fat, 2% fibre, 3% ash.

(Using Modified Atwater Factors for a commercial food.)

1. 100 — 12 — 10 — 2 — 3 — 70 = 3%NFE

2. ME protein: 12 × 3.5 = 42kcal/100g

   ME fat: 10 × 8.5 = 85kcal/100g

   ME NFE: 3 × 3.5 = 10.5kcal/100g

3. 42 + 85 + 10.5 = 137.5kcal/100g food

The ME of this food is 137.5kcal/100g (or 1,375kcal/kg).

Calculating the Calorie Distribution of a Dog Food

The metabolizable energy (ME) of food is usually expressed in kcal per kg of food (kcal/kg) or kcal per 100g (kcal/100g) and reflects the amount of energy-providing nutrients in the food. The levels of these nutrients can be shown as a percentage of the total ME in the diet or as grams of nutrient per 1,000 kcal ME.

When shown as a percentage of total ME, this is known as the calorie distribution of food. It is useful for determining how much energy is provided by each nutrient type and for choosing a food that is either calorie-dense (i.e., provides maximum energy in a small amount, typically through a high percentage of energy from fat) or calorie-dilute (i.e., provides a minimum amount of energy in a reasonable food portion, usually achieved through higher percentages of carbohydrate and/or protein in the diet).

Calculating calorie distribution is useful for assessing the suitability of a diet for different purposes. Diets for active and growing dogs should have more calories from fat, while weight management diets should have more calories from carbohydrates and proteins. To calculate the calorie distribution of a diet, you first calculate the total ME of the diet using the previous method and then determine what proportion of that ME is provided by fat, protein, and carbohydrates.

Using the earlier example of a wet dog food with a calculated ME of 137.5 kcal/100g, where 42 kcal/100g came from protein, 85 kcal/100g from fat, and 10.5 kcal/100g from NFE, the calorie distribution can be calculated as follows (note that values have been rounded for ease):

1. Calculate the percentage of total calories from protein (ME protein/total ME),

   e.g. (42 ÷137.5) × 100 = 30%

2. Calculate the percentage of total calories from fat (ME fat/total ME),

   e.g. (85 ÷ 137.5) × 100 = 62%

3. Calculate the percentage of total calories from NFE (ME NFE/total ME),

   e.g. (10.5 ÷ 137.5) × 100 = 8%

4. Check by addition that the percentages equal 100%,

   e.g. 30 + 62 + 8 = 100%

The calorie distribution of food is often best presented as a pie chart.

A pie chat is often used to visually represent the percentage calorie distribution of a diet.

Maintenance Energy Requirements (MER) and Daily Energy Requirements (DER) of Dogs

The maintenance energy requirement (MER) represents the minimum amount of energy that a dog requires each day from its food. It is important to note that the MER can vary depending on individual factors such as age, spay/neuter status, activity level, breed, personality, and housing conditions. For instance, older and sedentary dogs typically have a lower MER compared to active, growing, or pregnant/lactating dogs. Spayed and neutered dogs also have an MER that can be 25 percent less than a reproductive entire dog of the same age. Additionally, some breeds, such as Jack Russell terriers, vizslas, flat coat retrievers, and bearded collies, may have higher energy requirements than others, such as Airedale terriers, golden retrievers, and West Highland white terriers.

Alternatively, the daily energy requirement (DER) can be used to estimate the energy needs of active adult dogs. This method considers the dog's activity level and breed as key determining factors instead of age. It is worth noting that different breeds and types may have varying energy requirements, with bearded collies, for instance, tending to have higher requirements than other breeds.

The West Highland white terrier is an example of a breed that typically has a lower dietary energy requirement than others.

It is feasible to compute the MER or DER of your canine companion to estimate the required caloric intake. However, it is important to note that in certain instances, the calculated values may not necessarily align with the specific needs of your dog. Therefore, it is crucial to exercise flexibility and closely monitor their activity to ensure that they maintain a healthy body weight and condition.

How to Calculate Your Dog’s MER – Useful for Sedentary Pet Dogs

The calculation of MER is determined by the metabolic bodyweight of your canine companion. This weight is calculated by raising their bodyweight in kilograms to the power of 0.75 (kg0.75) and is typically lower than their actual bodyweight. This can be easily determined using the scientific function on a calculator. Once the metabolic bodyweight has been determined, it is then multiplied by a factor that takes into account the age of the dog. For older dogs, the metabolic bodyweight is multiplied by 95, while for younger dogs, the value used to multiply the metabolic bodyweight is 130. Various multiplication values are available to account for individual dog age variations.

Reference table of factors for MER calculations

(Adapted from: FEDIAF Nutritional Guidelines for Complete and Complementary Pet Food for Cats and Dogs , 2021)

Worked Example of MER Calculation

This is Bertie, a 15kg, two-year-old, entire male, cocker spaniel. He is highly active and partially kennelled during the day but sleeps in the house at night. He is in a good, lean condition with a body condition score of 4 on a 9-point scale (where 9 is grossly obese).

Bertie.

• Bertie’s metabolic bodyweight is:

  150.75 = 7.62kg

• Using data from reference tables for MER based on age, the multiplication factor chosen is 130.

• Bertie’s calculated MER (ME/day):

  130 × (15)0.75 = 990kcal

Notably, Bertie actually gets fed somewhere between 200 and 500 extra calories per day based on his activity level in order to support a lean, healthy body condition, but this calculation is a starting point for assessing his dietary energy needs.

Calculating Daily Energy Requirements (DER) – Useful for Active Dogs

The Minimum Energy Requirement (MER) is the fundamental energy needed by your dog to maintain body functions and basic activity. However, it is important to note that MER calculations do not take into account the activity level, breed, or predisposition to obesity in individual dogs. To address this, a more effective approach is to calculate their Daily Energy Requirements (DER).

DER is calculated similarly to MER, using multiplication factors based on activity level. Activity is categorized into five different levels, each with descriptions of intensity, frequency, and duration. Some breeds, such as Newfoundlands and Great Danes, have breed-specific differences that result in different multiplication factors for their DER. Additionally, there is a multiplication factor that can be used for adult dogs that are prone to obesity. By using this method, an estimation of the number of kilocalories required for your dog's diet can be determined on a daily basis.

Reference table of factors for DER calculations

(Adapted from: FEDIAF Nutritional Guidelines for Complete and Complementary Pet Food for Cats and Dogs, 2021)

Worked Example of DER Calculation

Introducing Bobbi, a seven-year-old spayed female cocker spaniel weighing 14.5kg. As a highly active working gundog, she spends two to three days per week in the winter months working for four to six hours per day in cold and wet conditions. Despite her tendency to lose weight quickly and her anxious personality, Bobbi maintains a good, lean condition with a body condition score of 3.5 on a 9-point scale, where 9 indicates obesity.

• Bobbi’s metabolic bodyweight is:

  14.50.75 = 7.43kg

• Using data from reference tables for DER based on activity level, the multiplication factor chosen is 175 (the upper value chosen because of her temperament and body condition).

• Bobbi’s calculated MER (ME/day):

  175 × (14.5)0.75 = 1300 kcal

Bobbi's dietary intake currently consists of 1300 kcal per day, which has proven effective in maintaining her body condition. In the event of an increase in workload or frequency, her daily energy requirements (DER) will be assessed and her diet will be modified accordingly.

Bobbi.

How to Use the MER and DER Calculations

Calculating either MER or DER is an important step in determining the appropriate amount of kilocalories (i.e. energy) your dog needs from their food. This process can aid in making informed decisions about what to feed and the appropriate quantity. The availability of information about the food ME, either on the packaging or from the manufacturer/formulator, is crucial in this calculation. Alternatively, an approximate ME of the food can be calculated.

In general, for most pet dogs, MER is a reliable method of estimating their daily energy needs. However, for very active dogs or those with energetic or anxious personalities, DER is a more suitable approach. Measuring, monitoring, and managing your dog’s diet, energy intake, bodyweight, condition, and performance are essential in determining the best approach for your individual situation.

Feeding commercial food with clear feeding guidelines will be based on these calculations. It is worth noting that commercial feeding guides often suggest a wide range of possible amounts to be fed to account for nutritional individuality and the possible range in MER or DER requirements.

It is possible that your dog may have a healthy, lean bodyweight and body condition, and these calculations may not be necessary. However, an understanding of energy-requirement calculations may prove useful should your dog's circumstances ever change.

Summary

• Adequate and consistent energy supply is essential to support vital life processes and physical activity. Therefore, the dietary requirements of an animal must prioritize energy needs before considering other nutrient requirements.
• The energy content of a diet is determined by the amount of metabolizable energy (ME) it provides and is typically measured in kilocalories (kcal).
• While protein, fat, and carbohydrates all serve as dietary energy sources, fat provides more than twice the calories of protein or carbohydrates.
• Calculating the ME content of food and calorie distribution can help determine the suitability of a diet for individual dogs.
• A dog's energy requirements vary throughout their life and depend on various factors such as biology, growth, health, activity level, and housing conditions.
• MER (maintenance energy requirement) calculations can estimate the energy needs of sedentary dogs, while DER (daily energy requirement) calculations can determine the energy needs of more active dogs.