Energy Density of Pet Food and Energy Needs

Estimating Energy Density of the Food

Manufactured pet foods may provide this information on package labels, or it may be available through ‘off pack’ materials such as web sites, or on request from customer care services. In the U.S.A., calorie content statements are now required on all pet food labels, including those for treats and supplements. Information on the label must be provided in terms of kcal/kg and kcal per common unit (e.g., cups, cans, pieces). To use the formula above, the value in kcal/kg must be divided by 10 to provide the energy density in terms of kcal/100 g. If this information is not available it can be calculated indirectly from the amounts of macronutrients (protein, fat and carbohydrate), and fibre in the food. The equation to calculate energy content is quite complex and there are tools available that help avoid the need to manually calculate it.

Estimating the energy content of home-made foods can be a challenge. It requires access to reliable published information on the nutritional content of food ingredients commonly used in pet foods , or human foods and the ability to quantify the relative contribution of each ingredient to the total daily intake of each nutrient. This may require access to complex databases and software, or seek advice from a veterinary nutritionist that can assess the nutritional value of home-made diets. This is a significant disadvantage in feeding foods prepared at home.

Estimating Energy Needs

The specific energy need of an individual pet can be estimated using a mathematical equation that relates energy requirements to bodyweight , and in most species (including dogs and cats) this is best estimated from an exponential equation based on bodyweight . It is important to note that different equations exist for healthy adult dogs and cats, puppies, kittens, gestating or lactating mothers, and overweight pets .

In addition to bodyweight, there are a number of other factors that influence the energy requirement of the animal. These include activity, life-stage, reproductive status, and environmental conditions. Activity level can contribute to more than 30% of the daily energy requirement in highly active working dogs, such as Border Collies . However, recent studies have shown that adult pet dogs are relatively ‘inactive’ receiving on average only 4 walks of 40 minutes duration per week . The energy requirement of inactive dogs is lower than their active counterparts and this represents a more realistic starting point for most adult pet dogs and cats.

Equations to calculate energy requirements can be complex and cumbersome to use (table 1). Using these equations, energy requirements have been calculated for adult dogs, adult cats, puppies and kittens (link to excel file) references in table

Table 1. Equations to estimate energy requirements (ER) of dogs and cats.
Adult Dogs	Adult Cats
Based on inactive adult dogs ER = 95 x W0.75 kcal/d Where: W = actual body weight	ER = 77.4 x W0.711 kcal/d Where: W = actual body weight
Puppies After Weaning	Kittens After Weaning
ER = 130 x W0.75 x 3.2 x [e (-0.87p) – 0.1] kcal/d Where: W = actual body weight, Wm = predicted mature adult weight p = W/Wm e = base of natural log ~2.718	Step 1: ME = 100W0.67 X 6.7[e-0.189p – 0.66] kcal/d Step 2: ER = ME X 6.7[e-0.189p – 0.66] kcal/d Where: W = actual body weight p = W/Wm Wm = expected mature body weight

Calculating Food Allowances

Food allowances can be calculated, based on these energy requirements by entering the energy density of the food in this tool (link to excel food allowances). To convert the amount in grams per day from the tool to cans or trays per day, divide the g/d as calculated for that animal by the net weight of the can or tray in grams. To determine cups per day of a dry food, the density of the food in terms of grams per cup must be known. If that information is not provided as part of the calorie content statement as required under AAFCO model regulations, it can be calculated by dividing the kcal/cup value by the kcal/kg value, then multiplying the result by 1000 to give you g/cup. The pet's food allowance in g/d is then divided by g/cup to give you cups/d. There is no standard international cup size, in the United States of America, a standard measuring cup is 8 fluid ounces (approximately 237 mL) by volume, however in other countries, different volumes or weights of typical dry ingredients are used to determine a cup unit.

Responsible Feeding

Portion control is a cornerstone of responsible feeding, and feeding guides help owners ensure that they are feeding the correct amount of food to their pet. The feeding guide should be used as the foundation for estimating how much food to offer, but the exact amount should be tailored to meet the individual needs of the animal. To maintain a ‘healthy’ bodyweight, animals should be fed according to their ‘ideal’ body weight if known, which may not be their ‘current’ bodyweight. In addition regular monitoring of bodyweight, along with additional nutritional assessments such as body condition scoring (WSAVA Nutrition Toolkit, FEDIAF Nutritional Guidelines) will help detect early changes, and inform adjustments in the food allowance, to ensure the pet stays at their ‘ideal’ bodyweight.