371 Tryptophan requirements in small medium and large breed adult dogs using the indicator amino acid oxidation technique.

摘要

Tryptophan (Trp) is an indispensable amino acid for dogs of all life stages; however, while requirements for growing dogs are extrapolated from two dose-response studies, there is no empirical data on Trp maintenance requirements for adult dogs. Current recommended maintenance Trp requirements for adult dogs are based off the lowest dietary Trp level in a low-protein diet fed to a single breed over a 4-year period. The objective of this study was to determine Trp requirements in adult dogs of 3 different breeds using the indicator amino acid oxidation (IAAO) technique. Four spayed or neutered Dachshunds (5.28 ± 0.29 kg), 4 spayed Beagles (9.32 ± 0.41 kg), and 5 neutered Labrador Retrievers (30.51 ± 2.09 kg) were used. After a 14-day adaptation to a semi-purified diet, dogs were fed a mildly Trp-deficient diet supplemented with different isonitrogenous Trp-Ala solutions (final Trp levels were 0.082, 0.112, 0.132, 0.162, 0.192, 0.222, and 0.252 % as-fed). After a 2-day adaptation to the experimental diet, dogs underwent IAAO studies. During IAAO study days, feed was divided in 13 equal meals; at the sixth meal, dogs were fed a bolus of L-[1- C]-Phe (9.4 mg/kg BW), and thereafter, L-[1- C]-Phe was supplied with every meal (2.4 mg/kg BW). Total CO production during isotopic steady state was determined by enrichment of CO in breath samples and total CO production (measured using indirect calorimetry). Mean requirements for Trp and upper 95 % confidence intervals (CI) were determined using 2-phase linear regression models. Mean Trp requirements were estimated at 20.6, 38.8, and 20.9 mg/kg BWand CI were 25.0, 47.9, and 27.2 mg/kg BW for Dachshunds, Beagles, and Labradors, respectively. In conclusion, estimated Trp requirements are higher for Beagles compared to Labradors or Dachshunds, and all estimated requirements are higher than those currently recommended by the NRC (2006) and AAFCO (2018).