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→Dietary Sources
==Dietary Sources==
==Dietary Sources==
Foods differ in the amount of energy, and this is a primarily a function of the amount of moisture, digestibility, and the amount and proportions of macronutrients. Digestibility (i.e., feeding) studies are the most accurate way of determining the ‘available’ energy content of a food, but these studies are expensive and require the use of laboratory animals. Many pet food companies do not have the resources to conduct digestibility studies and use predictive equations instead. There are different predictive equations for pet foods and human foods, which in part reflects differences in the digestibility of these foods. Typically for highly digestible human foods such as chicken breast, egg, rice or oils, the [[Nutrition Glossary#Atwater Factors|‘Atwater’ factors]] [protein (4 kcal per gram), fat (9 kcal per gram), and carbohydrate (4 kcal per gram)] can be used to calculate energy content. Two different approaches are commonly used for estimating the energy content of manufactured pet foods. One uses pet foods the [[Nutrition Glossary#Modified Atwater Factors|modified Atwater factors]] of 3.5 kcal per gram of protein, 8.5 kcal per gram of fat, and 3.5 kcal per gram of carbohydrates. Whilst this equation is mathematically simple it has limitations, because it can over and underestimate foods with a digestibility that is lower or higher than ‘average’. An alternative but more complex equation which does account for differences in digestibility has been developed and this does appear to provide a better estimate of the ‘available’ energy content of the food.17
'''Foods differ in the amount of energy, and this is a primarily a function of the amount of moisture, digestibility, and the amount and proportions of macronutrients'''. Digestibility (i.e., feeding) studies are the most accurate way of determining the ‘available’ energy content of a food, but these studies are expensive and require the use of laboratory animals. Many pet food companies do not have the resources to conduct digestibility studies and use predictive equations instead. There are different predictive equations for pet foods and human foods, which in part reflects differences in the digestibility of these foods. Typically for highly digestible human foods such as chicken breast, egg, rice or oils, the [[Nutrition Glossary#Atwater Factors|‘Atwater’ factors]] [protein (4 kcal per gram), fat (9 kcal per gram), and carbohydrate (4 kcal per gram)] can be used to calculate energy content.
*Step 1 calculate carbohydrate (NFE) content: Carbohydrate (NFE; g/100g)) = 100 - (Moisture + Protein + Fat + Ash + Crude Fibre)
*Step 2 calculate the Gross Energy (GE) content of the food: GE (kcal/100g) = (5.7 x protein) + (9.4 x fat) + (4.1 x [NFE + Crude Fibre])
Two different approaches are commonly used for estimating the energy content of manufactured pet foods. One uses pet foods the [[Nutrition Glossary#Modified Atwater Factors|modified Atwater factors]] of 3.5 kcal per gram of protein, 8.5 kcal per gram of fat, and 3.5 kcal per gram of carbohydrates. Whilst this equation is mathematically simple it has limitations, because it can over and underestimate foods with a digestibility that is lower or higher than ‘average’. An alternative but more complex equation which does account for differences in digestibility has been developed and this does appear to provide a better estimate of the ‘available’ energy content of the food.17
*Step 3 calculate the percentage digestibility of the food (there are different equations for cat and dog foods)
*'''Step 1:''' calculate carbohydrate (NFE) content: Carbohydrate (NFE; g/100g)) = 100 - (Moisture + Protein + Fat + Ash + Crude Fibre)
*'''Step 2:''' calculate the Gross Energy (GE) content of the food: GE (kcal/100g) = (5.7 x protein) + (9.4 x fat) + (4.1 x [NFE + Crude Fibre])
*'''Step 3:''' calculate the percentage digestibility of the food (there are different equations for cat and dog foods)
:*Cat, % digestibility of energy = 87.9 – (0.88 x CF x 100/[100- % moisture])
:*Cat, % digestibility of energy = 87.9 – (0.88 x CF x 100/[100- % moisture])
:*Dog, % digestibility of energy = 91.2 – (1.43 x CF x 100/[100- % moisture])
:*Dog, % digestibility of energy = 91.2 – (1.43 x CF x 100/[100- % moisture])
*Step 4: calculate DE content: DE = GE (from step 2) x % energy digestibility (from step 3)/100
*'''Step 4:''' calculate DE content: DE = GE (from step 2) x % energy digestibility (from step 3)/100
*Step 5: calculate ME content (there are different equations for cat and dog foods)
*'''Step 5:''' calculate ME content (there are different equations for cat and dog foods)
:*Cat ME (kcal/100g) = DE (from step 4) – (0.77 x protein g)
:*Cat ME (kcal/100g) = DE (from step 4) – (0.77 x protein g)
:*Dog, ME (kcal/100g) = DE (from step 4) – (1.04 x protein g)
:*Dog, ME (kcal/100g) = DE (from step 4) – (1.04 x protein g)
Key:
'''Key:'''
GE = gross energy (DE = digestible energy; DE = digestible energy; ME = metabolisable energy; CF = crude fibre; NFE = nitrogen free extract
*GE = gross energy
*DE = digestible energy
*DE = digestible energy
*ME = metabolisable energy
*CF = crude fibre
*NFE = nitrogen free extract
The specific energy contribution of a commercial pet food on an as-fed basis will also depend on dietary moisture level: dry food (<14% moisture) provide between 330-380+ kcal per 100g; semi-moist (>14% and <60% moisture) provide between 250-350+ kcal per 100g; and wet food (>60% moisture) typically provide 80-100+ kcal per 100 g. Since fat provides a larger proportion of energy relative to protein and carbohydrates, diets with higher fat levels will provide more energy per 100g as-fed. The energy contribution of total dietary fibre is negligible for dogs and cats, yet inclusion of high levels of dietary fibre, especially insoluble, non-fermentable fibre will increase volume of food while decreasing energy content.18,19
The specific energy contribution of a commercial pet food on an as-fed basis will also depend on dietary moisture level:
*Dry food (<14% moisture) provides between 330-380+ kcal per 100g;
*Semi-moist (>14% and <60% moisture) provides between 250-350+ kcal per 100g;
*Wet food (>60% moisture) typically provides 80-100+ kcal per 100 g.
'''Since fat provides a larger proportion of energy relative to protein and carbohydrates, diets with higher fat levels will provide more energy per 100g as-fed'''. The energy contribution of total dietary fibre is negligible for dogs and cats, yet inclusion of high levels of dietary fibre, especially insoluble, non-fermentable fibre will increase volume of food while decreasing energy content.18,19
==Diagnosing Energy Deficiency==
==Diagnosing Energy Deficiency==