Feeding Guides - Nutrition

Introduction

Most pet foods provide owners with guidance on how much, and sometimes how often they should feed their dog or cat. The amount of food a pet needs is a function of the energy content of the food and the energy requirement of the pet. Feeding guides should be used as starting point to estimate how much food to offer. Because energy requirements differ among animals, and can also vary within a cat or dog over time, the exact amount to feed must be tailored according to the needs of the individual.

Feeding Guides on Pet Food

Most commercially manufactured pet foods provide feeding guides on the packaging. This is a mandatory requirement for those that are complete and balanced. The key principles and steps used to calculate food allowances are described in the next section. Understanding how these principles are applied is important, as they determine how much food and energy a pet is advised to eat.

There is no international standard defining how feeding guides are calculated, and manufacturers may take different approaches, and make different assumptions on how they do this. Different products may recommend feeding different amounts of energy for the same pet, and can result in either an over or under-estimate of their ‘actual’ energy needs.

There is also no standard way in which feeding guidelines are presented on the packaging. For example, dry foods may describe serving amounts by weight (grams per serving), or volume (cup), or both. Wet foods generally describe serving amounts by volume i.e. as fraction and/or multiple of a can, pouch or tray.

The limited physical space available on package labels constrains how much information can be included, and this is a particular challenge for dog products because of the wide size range that needs to be covered. For example, some products provide guidance for discreet weight ranges (table 1), whereas others to do this for specific weights (table 2). In both circumstances, owners may need to extrapolate to estimate a food allowance if the weight of their pet falls between these ranges.

TABLES

How Feeding Guides Are Calculated

Feeding guides are calculated by dividing the pet’s daily energy requirements by the energy density of the food, following the 2 step approach outlined in figure 1 .

Figure 1 – How feeding guides are calculated

Step 1

• Calculate the pet’s energy needs per day (kcal/d)

• Determine the energy density of the food (kcal/100 g diet)

Step 2

• Calculate daily amount of food (g/d) = [Pet energy needs (kcal/d) x 100]/Energy density of the food (kcal/100 g)

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., 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 (link to WikiVet nutrition section). The equation to calculate energy content is quite complex and there are tools available that help avoid the need to manually calculate.

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 total daily intake of each nutrient. This may require access to complex databases and software, or seek advice from an independent expert that can assess the nutritional value of home-made diets link . This is a significant disadvantage in feeding foods prepared at home (link to section on home prepared foods)

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 , and link to energy section).

In addition to bodyweight, there are a number of other factors that influence the energy requirement of the pet. 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 2). Using these equations, energy requirements have been calculated for adult dogs, adult cats, puppies and kittens (link to excel file)

TABLES

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 pet. To maintain a ‘healthy’ bodyweight, pets should be fed according to their ‘ideal’ body weight, which may not be their ‘current’ bodyweight. In addition regular monitoring of bodyweight, along with additional nutritional assessments such as body condition scoring (PFMA Size-o-meter; ) will help detect early changes, and inform adjustments in the food allowance, to ensure the pet stays at their ‘ideal’ bodyweight.