The objective of this study was to determine the minimum requirement (MR) for methionine (Met), when cyst(e)ine (Cys) is provided in excess, in adult dogs of three different breed sizes using the indicator amino acid (AA) oxidation (IAAO) technique. In total, 12 adult dogs were used: 1 neutered and 3 spayed Miniature Dachshunds (4.8 ± 0.4 kg body weight [BW], mean ± SD), 4 spayed Beagles (9.5 ± 0.7 kg BW, mean ± SD), and 4 neutered Labrador Retrievers (31.8 ± 1.7 kg BW, mean ± SD). A deficient Met basal diet with excess Cys was formulated. Dogs were fed the basal diet randomly supplemented with different Met-Alanine (Ala) solutions to achieve final Met concentrations in experimental diets of 0.21%, 0.26%, 0.31%, 0.36%, 0.41%, 0.46%, and 0.66% (as-fed basis). After 2 d of adaptation to the experimental diets, dogs underwent individual IAAO studies. During the IAAO study day, the total feed was divided into 13 equal meals; at the sixth meal, dogs were fed a bolus of l-[1-¹³C]-phenylalanine (Phe), and thereafter, l-[1-¹³C]-Phe was supplied with every meal. The total production of ¹³CO₂ during isotopic steady state was determined by the enrichment of ¹³CO₂ in breath samples, and the total production of CO₂ measured using indirect calorimetry. The mean MR for Met and the upper 95% confidence limit (CL) were determined using a two-phase linear mixed-effects regression model. For Miniature Dachshunds, the MR for Met was between the first two dietary Met concentrations and is, therefore, between 35.7 and 44.1 mg.kg BW⁻¹·d⁻¹ (0.21% to 0.26%, as-fed basis; no requirement could be determined on a metabolic BW basis). For Beagles and Labrador Retrievers, the MR for Met was 57.5 and 50.4 mg.kg BW⁻¹·d⁻¹, 107.7 and 121.8 mg/kg BW^{^0.75}, or 0.338 and 0.360%, respectively (as-fed basis). The upper 95% CL of Met requirements was 77.9 and 72.4 mg.kg BW⁻¹·d⁻¹, 147.8 and 159.6 mg/kg BW^{^0.75},or 0.458 and 0.517% for Beagles, and Labradors, respectively (as-fed basis). When pooling data from Beagles and Labrador Retrievers, the MR and upper 95% CL were 56.0 and 75.8 mg.kg BW⁻¹·d⁻¹ or 118.4 and 150.5 mg/kg BW^{^0.75} or 0.360% and 0.482% (as-fed basis). In conclusion, the MR and the upper 95% CL for Met are different for Dachshunds when compared with Beagles and Labrador Retrievers. Using this low-protein diet, the estimated upper 95% CL Met requirement for Beagles and Labrador is higher than those recommended in the National Research Council (NRC), but NRC is similar to the estimated upper 95% CL for Dachshunds.

中文翻译：

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使用指示剂氨基酸氧化技术的小型腊肠犬，小猎犬和拉布拉多犬成年犬的最低饮食蛋氨酸需求量

这项研究的目的是使用指示剂氨基酸（AA）确定三种不同品种大小的成年犬中过量提供胱氨酸（Cys）时蛋氨酸（Met）的最低需求（MR）。氧化（IAAO）技术。总共使用了12只成年犬：1头绝育犬和3头小腊肠犬（体重4.8±0.4千克[ BW]，平均值±SD），4头小猎犬（9.5±0.7 kg BW，平均值±SD）和4根绝育的拉布拉多猎犬（31.8±1.7 kg BW，平均值±SD）。配制了不足的半胱氨酸Met基础饮食。用随机补充不同Met-丙氨酸（Ala）溶液的基础饮食喂狗，以使实验饮食中的最终Met浓度达到0.21％，0.26％，0.31％，0.36％，0.41％，0.46％和0.66％（as-联邦基础）。在适应实验饮食2天后，对狗进行了单独的IAAO研究。在国际民航组织研究日期间，将总饲料分成13份等餐。在第六餐，狗饲喂的丸药升- [1- ¹³ C] -苯丙氨酸丙氨酸（Phe），其后，升- [1- ¹³ C] -Phe用每餐提供。总生产¹³ CO ₂中的同位素稳定状态是由富集确定¹³ CO ₂的呼吸样本中，总生产CO的₂使用间接量热法测量。使用两阶段线性混合效应回归模型确定Met的平均MR和95％置信上限（CL）。对于小型腊肠犬，Met的MR在前​​两个饮食Met浓度之间，因此介于35.7和44.1 mg.kg BW ^-1 ·d ^-1之间（按进食量计算为0.21％至0.26％；没有要求）根据代谢性体重确定）。对于小猎犬和拉布拉多犬，大都会的MR为57.5和50.4 mg.kg BW ^-1 ·d^-1，107.7和121.8毫克/公斤体重^{^ 0.75}分别或0.338和0.360％，（如喂养的基础上）。满足Met要求的最高95％CL分别为77.9和72.4 mg.kg BW ^-1 ·d ^-1，分别为147.8和159.6 mg / kg BW ^{^ 0.75}，Beagles和Labradors分别为0.458和0.517％（按进给基准计） ）。汇总比格犬和拉布拉多犬的数据时，MR和最高95％CL分别为56.0和75.8 mg.kg BW ^-1 ·d ^-1或118.4和150.5 mg / kg BW ^{^ 0.75}或0.360％和0.482％（按月计算）。总之，与小猎犬和拉布拉多犬相比，腊肠犬的MR和最高95％CL均不同。使用这种低蛋白饮食，比格犬和拉布拉多犬的最高95％CL CL估计需求高于国家研究委员会（NRC）推荐的水平，但NRC与腊肠犬的最高95％CL相似。