Abstract
Abstract Over time, the need to update amino acid requirements for canines is increasingly important due to genetic selection and the demand for more advanced diets. Amino acid requirements can be determined through differing methods including, but not limited to, nitrogen balance studies and the indicator amino acid oxidation (IAAO) technique. In this study, the IAAO method was studied on a total of six growing Labrador Retrievers to determine their individual amino acid requirements. Twelve test diets with varying levels of Arg were utilized to conduct this experiment. Six diets contained excess Lys with respect to Arg (Group 1), while the remaining diets contained lower Lys inclusions (Group 2). Diets were formulated to 1.6x NRC values for all indispensable amino acids, including Lys. Group 2 diet formulations were formulated the same as Group I, except the test Lys was set at 0.1% above test Arg levels. The control diet was fed for two days, followed by a day in which the test diet was fed, a tracer amino acid was supplied, and breath samples were collected. On test day, a priming dose of L-[1-13C]phenylalanine (Cambridge Isotope Laboratories, Inc.) based on the subject’s body weight was first supplied, followed by [1-13C]Phe doses every thirty minutes, spanning a four hour period. A respiration mask was placed on each subject every thirty minutes (Oxymax, Columbus Instruments), 13CO2 was collected, and enrichment was determined by isotope ratio mass spectrometry (IRMS). Results for IRMS were converted to atom percent excess (APE) and analyzed using a piecewise model of best fit (JMP Pro 14.1). Through the segmented line regression, the arginine mean requirement and population safe requirements of growing dogs in Groups 1 and 2 was found to be 1.49 ± 0.30 and 1.38 ± 0.21 g/1000 kcal ME (mean ± 2SD), respectively.
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