Page 117 - Raw Diet References Book 2019

2.2.1 Gross energy

The gross energy (GE) of a food is defined as the total 2006a). The predicted GE values of protein, fat and
chemical combustible energy arising from complete carbohydrate are listed in table VII-5.
combustion of a food in a bomb calorimeter (NRC

Table VII-5.

Predicted gross energy values of protein, fat and carbohydrate

Nutrient Gross Energy

Crude protein 5.7kcal/g 23.8kJ/g

Fat 9.4kcal/g 39.3kJ/g

NFE + Crude fibre 4.1kcal/g 17.1kJ/g

(Kienzle et al. 2002; NRC 2006a) NFE = nitrogen free extract

2.2.2 Metabolizable energy

Digestible energy and metabolizable energy are a years, and their accuracy and precision have been
more accurate way of expressing the energy density compared to those of equations developed from
of a food. Metabolizable energy reflects better the animal feeding studies. Within the Petfood industry
energy that is utilised by the animal, but is more the most commonly used predictive equations
difficult to determine. The metabolizable energy for prepared pet foods are the “modified Atwater”
(ME) of a pet food is measured most accurately by equation and two equations (one for dog foods and
performing digestibility trials using one of the two one for cat foods) cited by the National Research
methods described in Chapter VI. Since animal studies Council (NRC, 2006). However, there is currently no
are labour intensive, predictive equations are used uniformity as to their use. Considering the labelling
extensively for calculating metabolizable energy (ME) declarations required for certain pet food products
concentrations of dog and cat foods. Several of these listed in Annex I to Directive 2008/38/EC it is clear that
predictive equations have been developed during the there is a need for harmonisation at EU level.

a) Predictive Equations for ME in prepared foods for dogs and cats

a ) Modified Atwater factors For processed pet based on an average digestibility of 90% for fat, 85% for
1
food “modified” Atwater factors can be used; they are carbohydrate (NFE) and 80% for protein (NRC 1985b).

kcal ME /100g = % crude protein x 3.5 + % crude fat x 8.5 + % NFE x 3.5 (AAFCO 2008)

kJ ME /100g = % crude protein x 14.65 + % crude fat x 35.56 + % NFE x 14.65

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