Protein and amino acid bioavailability estimates for canine foods

Estimates of nutrient bioavailability are required for establishing dietary nutrient requirements and to evaluate the nutritional value of food ingredients or foods that are exposed to processing or extended storage. This study aimed to generate estimates for the bioavailability of dietary CP and AA for adult dogs using existing literature data and to evaluate the accuracy of estimates currently used in 3 authoritative publications. A regression equation was derived relating apparent fecal N outflow to standardized ileal N outflow from a data set containing information on 158 individual diets and their N digestibility when fed to adult dogs. Standardized ileal digestibility (sID) of N (sID) was shown to be nearly perfectly correlated to the sID of the sum of N of AA in 24 diets for which AA digestibility data were available. Regression equations between sID of individual AA and sID were calculated. Bioavailability estimates were subsequently derived from simulated sID values of N and essential and nonessential AA for 10 diets varying in CP content (18 to 42%) and apparent fecal N digestibility (70 and 80%) for an adult dog of 20 kg BW. Calculated bioavailability estimates of the NRC for maintenance dog foods do not lead to realistic nutrient allowance estimates for CP and AA. Estimates used by the Association of American Feed Control Officials and the European Pet Food Industry Federation were closer to calculated values, although the majority were too low, with the exception of CP, Arg, and Lys. Bioavailability estimates for Lys, Met, and Cys as calculated here require further veracity as the chemical form in which these AA are present in commercial pet foods may significantly reduce their bioavailability.