Department of Animal Biosciences, University of Guelph, Guelph, Ontario, Canada.
Procter & Gamble Co., Mason, OH.
J Anim Sci. 2019 Jul 30;97(8):3274-3285. doi: 10.1093/jas/skz142.
Tryptophan (Trp) is an indispensable amino acid (AA) for dogs of all life stages; however, although Trp requirements for growing dogs are derived from 3 dose-response studies, there are no empirical data on Trp requirements for adult dogs at maintenance. The study objective was to determine Trp requirements of adult dogs of 3 different breeds using the indicator amino acid oxidation (IAAO) technique. Four spayed or neutered Miniature Dachshunds (5.28 ± 0.29 kg BW), 4 spayed Beagles (9.32 ± 0.41 kg BW), and 5 neutered Labrador Retrievers (30.51 ± 2.09 kg BW) were used. After a 14-d adaptation to a Trp-adequate basal diet (Trp = 0.482% dry matter), all dogs were fed a mildly Trp-deficient diet for 2 d (Trp = 0.092% dry matter) before being randomly allocated to receiving 1 of 7 concentrations of Trp supplementation (final Trp content in experimental diets was 0.092, 0.126, 0.148, 0.182, 0.216, 0.249, and 0.283% dry matter) and all dogs received all Trp treatments. After 2-d adaptation to the experimental diets, dogs underwent individual IAAO studies. Total feed was divided in 13 equal meals; at the sixth meal, dogs were fed a bolus of L-[1-13C]-Phenylalanine (Phe) (9.40 mg/kg BW), and thereafter, L-[1-13C]-Phe was supplied (2.4 mg/kg BW) with every meal. Total production of 13CO2 during isotopic steady state was determined by enrichment of 13CO2 in breath samples and total production of CO2 measured using indirect calorimetry. The maintenance requirement for Trp and the 95% confidence interval (CI) were determined using a 2-phase linear regression model. Mean Trp requirements were estimated at 0.154, 0.218, and 0.157% (dry-matter) for Dachshunds, Beagles, and Labradors, respectively. The upper 95% CI were 0.187, 0.269, and 0.204% (dry-matter) for Dachshunds, Beagles, and Labradors. In conclusion, estimated Trp requirements are higher for Beagles compared with Labradors or Dachshunds, and all estimated requirements are higher than those currently recommended by the NRC and AAFCO.
色氨酸（Trp）是所有生命阶段犬的必需氨基酸（AA）；然而，尽管生长犬的 Trp 需要量来自 3 项剂量反应研究，但维持期成年犬的 Trp 需要量尚无实证数据。本研究旨在使用指示剂氨基酸氧化（IAAO）技术确定 3 种不同品种成年犬的 Trp 需要量。使用 4 只绝育迷你杜宾犬（5.28 ± 0.29 kg BW）、4 只绝育比格犬（9.32 ± 0.41 kg BW）和 5 只绝育拉布拉多猎犬（30.51 ± 2.09 kg BW）。在适应 Trp 充足基础日粮（Trp = 0.482%干物质）14d 后，所有犬连续 2d 饲喂轻度 Trp 缺乏日粮（Trp = 0.092%干物质），然后随机分配接受 7 种不同 Trp 添加浓度之一的处理（实验日粮的最终 Trp 含量为 0.092、0.126、0.148、0.182、0.216、0.249 和 0.283%干物质），所有犬都接受所有 Trp 处理。适应实验日粮 2d 后，犬进行个体 IAAO 研究。将总饲料分为 13 等份；在第 6 餐时，犬给予 L-[1-13C]-苯丙氨酸（Phe）（9.40 mg/kg BW）丸剂，此后每餐均供给 L-[1-13C]-Phe（2.4 mg/kg BW）。通过呼吸样本中 13CO2 的富集和间接测热法测量的 CO2 总产量来确定 13CO2 在同位素稳态时的总产量。使用 2 相线性回归模型确定 Trp 的维持需要量及其 95%置信区间（CI）。杜宾犬、比格犬和拉布拉多犬的平均 Trp 需要量估计值分别为 0.154%、0.218%和 0.157%（干物质）。杜宾犬、比格犬和拉布拉多犬的上限 95%CI 分别为 0.187%、0.269%和 0.204%（干物质）。总之，与拉布拉多犬或杜宾犬相比，比格犬的估计 Trp 需要量更高，所有估计的需要量都高于 NRC 和 AAFCO 目前推荐的需要量。
