Using Gross Energy Improves Metabolizable Energy Predictive Equations for Pet Foods Whereas Undigested Protein and Fiber Content Predict Stool Quality

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.

Cats Have Increased Protein Digestibility as Compared to Dogs and Improve Their Ability to Absorb Protein as Dietary Protein Intake Shifts from Animal to Plant Sources

“…Although protein adequacy requires the correct amino acids to be absorbed in their appropriate concentrations, the total tract protein digestibility is a valuable indicator of protein nutrition. The recommended minimum concentrations have been shown to be more than adequate with normal pet food ingredients in the dog [3] and the cat [4] in foods with protein digestibility similar to the averages reported by Hall et al [5].…”

Protein and amino acid bioavailability estimates for canine foods

“…Kendall et al (1982) reported mean values (n = 106) of 83, 84, and 77% for wet, intermediate, and dry commercial canine foods. Hall et al (2013) reported standardized total tract protein digestibility coefficients for 331 dry and moist canine foods of 89.7 and 88.0%, respectively. Expression to apparent digestibility values yields estimates that are approximately 6 percentage units lower.…”

“…Expression to apparent digestibility values yields estimates that are approximately 6 percentage units lower. Although the apparent digestibility values reported by Hall et al (2013) are approximately 83%, two-thirds of the foods were not commercially available and premium foods were overrepresented (D. E. Jewell, Hill's Pet Nutrition, Topeka, Kansas, personal communication). Although a value of 70% appears to be low, Hervera (2011) reported an aFD N value in commercial dog foods of 71%.…”

Commercially available avian and mammalian whole prey diet items targeted for consumption by managed exotic and domestic pet felines: Macronutrient, mineral, and long‐chain fatty acid composition

“…Despite being carnivores, dietary fibers and undigested proteins are important for maintaining gastrointestinal health and stool quality in cats. Dietary fiber promotes laxation and short‐chain fatty acid production as in other species [Hall et al, ; Kerr et al, ]. Feline hindgut microbiota are highly active and are capable of fermenting plant‐ and animal‐based substrates [Sunvold et al, ; Depauw et al, ], resulting in increased fecal short‐chain fatty acid concentrations and reduced fecal pH [Kerr et al, ].…”