PSLBI-16 Arginine requirements of young adult and senior Labrador retrievers

Consumer demand for diets that meet the age-appropriate nutritional needs of their pets has steadily risen in recent years as senior dogs represent an increasing proportion of the pet population. However, few studies have targeted the specific amino acid requirements of the aging canine. In this study, the indicator amino acid oxidation (IAAO) technique was used to compare the arginine (Arg) requirements of young adult and senior Labrador retrievers. After 2-d adaptation to Arg-adequate basal diet (Arg = 0.82% dry matter), dogs underwent individual IAOO studies. In brief, all dogs were randomly fed one of six test diets with varying levels of arginine ranging from deficient to sufficient (final Arg content in experimental diets was 0.25, 0.29, 0.33, 0.71, 0.77 and 0.82% dry matter. Test diet was divided into 13 equal meals; at the 5th meal, a tracer amino acid was supplied (a bolus L-[1-13C] phenylalanine based on body weight was first given, followed by [1-13C] Phe doses every 30 min spanning a 4-h period), and breath samples were collected via respiration mask every 30 min. Total production of 13CO2 during isotopic steady state was determined by enrichment of 13CO2 in breath samples and total CO2 production was measured via indirect calorimetry and isotope ratio mass spectrometry (IRMS). Results for IRMS data were converted to atom percent excess (APE) and analyzed using segmented linear regression. The Four Rivers mean and population requirements for arginine were 1,004 ± 90.5 mg/1,000 kcal ME (mean ± 2 SD) in young adults and 919 ± 69.9 mg/1,000 kcal ME for senior dogs, which are slightly greater than the currently recommended amounts by NRC. As the pet food industry offers more specialized diets for aging canines, updating the amino acid requirements for such animals is increasingly important.