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PSI-B-40 Late-Breaking: Determination of lysine requirements of young and senior Labrador retrievers using the indicator amino acid oxidation technique


 In order improve the health and longevity of canines, the need to determine amino acid requirements for aging populations is particularly important. In this experiment, a total of six young (< 1.5 yrs) and six old (>8 yrs) Labrador retrievers were studied in order to determine the lysine (Lys) requirement through the indicator amino acid oxidation (IAAO) technique. All dogs were supplied with constant dietary Phe in the control and test diets. 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 broken-line model of best fit (JMP Pro 14.1). The [1-13C] Phe oxidation results showed that the minimal requirement of the young adult and senior dogs was 1.08 ± 0.59 and 0.83 ± 0.12 (mean ± 2SD) g/1000 kcal ME, respectively. The lower lysine requirements for the senior dogs is due to the seniors having an average of 987g less lean mass per dog than the young adults.