Calories and Energetic Balance

 PLATINUM PAW MODULE 2

Calories and Energetic Balance

THE BASIC REQUIREMENT

Like us, your pet requires a balanced diet for normal growth during youth and maintenance once the pet is fully grown.  As we have learned in previous modules, specific requirements might change from liftstage to lifestage but the basic components remain the same. These include a basic energetic requirement and six other categories of nutrients, including: water, protein, fat, minerals, carbohydrates and vitamins. Although energy is not a nutrient per se, 50-80% of an animal’s food consumption is used for this purpose.

Plants obtain their energy from the sun and store it as carbohydrates. Animals obtain their energy from plants or animals and use this energy directly as a carbohydrate, or break it down and store it as fat. Energy is required for everything in your pet’s body, from going for a walk, to panting, to digestion and maintaining body tissues. This is important to know, as energy is always the first dietary requirement that will be met. Despite a pets need for essential amino acids and fats, the energy yielding nutrients will be used to replenish the energetic requirement before being used for any other purpose. Once the energetic requirements are met, additional nutrients will be used for everything else.

On most pet food labels, energy will be expressed in metabolizable energy (ME). This is the amount of energy that is available to tissues in the body after accounting for average losses in feces and urine.  ME is often expressed in units of kcal/kg.  Kcal is an abbreviation of kilocalories. A calorie is a unit that refers to the quantity of energy it takes to increase the temperature of 1 gram of water by 1˚C. A calorie is such a small unit it becomes impractical to use a calorie as a unit of energy. This is why most foods, human and pet, are expressed in kilocalories, which is equal to 1000 calories (or Calories with a capital ‘C’ on human foods).

The ME is specific to both the content of the food and the animal that is consuming it. This means that the ME of a food for a human would be different than the ME for the same food for a cat or a dog. There are many digestive and physiological reasons for this. The length of the gastrointestinal tract, or the presence of several stomachs can increase the ME of grass in a cow comparatively to what it would be in humans or pets. For example, the basic rules of energy in human are the following:

A digestibility coefficient is the proportion of the nutrient that is actually available for absorption and use by the body of the animal. 

From these numbers, you could calculate the number of kcal in the human food by knowing the protein, fat and carbohydrate content.  Consider the following protein bar:

However, of the same product was consumed by a pet; the actual energy content would be slightly different.

From these numbers, you could calculate the number of kcal in the human food by knowing the protein, fat and carbohydrate content.  Consider the following protein bar:

Humans are capable of getting more calories out of this product than your pet. This calculation for pets is useful in calculating the calories in homemade pet foods and commercial foods alike. How does this apply when dealing with percentages in the guaranteed analysis on pet foods? Let’s take the following analysis:

Guaranteed Analysis
Protein (min)                          32%
Fat (min)                                17%
Moisture (max)                       10%
Fibre (max)                             6%
Ash (max)                               6%
Carbohydrate (approx.)           29%
*Carbohydrate content is rarely provided on pet food labeling, we’ll learn how to calculate this in the next module.  For now, a value will be provided.

And apply what we have just learned.

Since this the calorie content for 100g and most pet foods list the ME by the kilogram, we must multiply our answer by 1000g/kg to get the proper value.

(358kcal/100g) x (1000g/kg) = 3580 kcal/kg

Now you know how the ME on pet food is calculated and have the ability to calculate the proportion of calories in pet food that come from all the major constituents: protein, fat or carbohydrates.