Abstract
Because animal studies are labor intensive, predictive equations are used extensively for calculating metabolizable energy (ME) concentrations of dog and cat pet foods. The objective of this retrospective review of digestibility studies, which were conducted over a 7-year period and based upon Association of American Feed Control Officials (AAFCO) feeding protocols, was to compare the accuracy and precision of equations developed from these animal feeding studies to commonly used predictive equations. Feeding studies in dogs and cats (331 and 227 studies, respectively) showed that equations using modified Atwater factors accurately predict ME concentrations in dog and cat pet foods (r2 = 0.97 and 0.98, respectively). The National Research Council (NRC) equations also accurately predicted ME concentrations in pet foods (r2 = 0.97 for dog and cat foods). For dogs, these equations resulted in an average estimate of ME within 0.16% and 2.24% of the actual ME measured (equations using modified Atwater factors and NRC equations, respectively); for cats these equations resulted in an average estimate of ME within 1.57% and 1.80% of the actual ME measured. However, better predictions of dietary ME in dog and cat pet foods were achieved using equations based on analysis of gross energy (GE) and new factors for moisture, protein, fat and fiber. When this was done there was less than 0.01% difference between the measured ME and the average predicted ME (r2 = 0.99 and 1.00 in dogs and cats, respectively) whereas the absolute value of the difference between measured and predicted was reduced by approximately 50% in dogs and 60% in cats. Stool quality, which was measured by stool score, was influenced positively when dietary protein digestibility was high and fiber digestibility was low. In conclusion, using GE improves predictive equations for ME content of dog and cat pet foods. Nondigestible protein and fiber content of diets predicts stool quality.
Highlights
Most pet owners in the United States feed their pets commercially prepared pet foods
Using the predictive equation with modified Atwater factors for dogs and cats (3.5 kcal/g protein, 8.5 kcal/g fat, and 3.5 kcal/g carbohydrate) as described by American Feed Control Officials (AAFCO) [4] to calculate metabolizable energy (ME) involves calculating a carbohydrate estimate for nitrogen-free extract (NFE), which is obtained by subtracting percent protein, fat, crude fiber, moisture, and ash from 100%
Animal feeding studies (331 in the dog and 227 in the cat), performed over a 7-year period that were based upon AAFCO feeding protocols, were reviewed to compare the accuracy and precision of equations developed from these digestibility studies to published predictive equations for ME concentrations in dog and cat pet foods
Summary
Most pet owners in the United States feed their pets commercially prepared pet foods. Fulfilling the nutrient requirements of pet animals with commercially prepared foods requires knowledge about the food as well as an understanding of the lifestage nutritional needs of the pet. To determine how much food to feed, one must know the energy density of the food. Dividing the energy requirement of the pet by the energy density of the food determines the daily amount to feed. Knowing the energy density of a food is important in determining the quantity of food that is offered each day. Because pets eat to maintain energy intake, energy density determines the amount of all other nutrients that a pet ingests. The non-energy nutrients in the food must be balanced relative to energy density to ensure adequate nutrient intake
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