Grain-based ingredients are replaced in part by pulse ingredients in grain-free pet foods. Pulse ingredients are lower in methionine and cysteine, amino acid (AA) precursors to taurine synthesis in dogs. Although recent work has investigated plasma and whole blood taurine concentrations when feeding grain-free diets, supplementation of a grain-free diet with various nutrients involved in the biosynthesis of taurine has not been evaluated. This study aimed to investigate the effects of supplementing a complete grain-free dry dog food with either methionine (MET), taurine (TAU), or methyl donors (choline) and methyl receivers (creatine and carnitine; CCC) on postprandial AA concentrations. Eight healthy Beagle dogs were fed one of the three treatments or the control grain-free diet (CON) for 7 d in a 4 × 4 Latin square design. On day 7, cephalic catheters were placed and one fasted sample (0 min) and a series of nine post-meal blood samples were collected at 15, 30, 60, 90, 120, 180, 240, 300, and 360 min. Data were analyzed as repeated measures using the PROC GLIMMIX function in SAS (Version 9.4). Dogs fed MET had greater plasma and whole blood methionine concentrations from 30 to 360 min after a meal (P < 0.0001) and greater plasma homocysteine concentrations from 60 to 360 min after a meal (P < 0.0001) compared with dogs fed CON, TAU, and CCC. Dogs fed TAU had greater plasma taurine concentrations over time compared with dogs fed CON (P = 0.02) but were not different than dogs fed MET and CCC (P > 0.05). In addition, most AAs remained significantly elevated at 6 h post-meal compared with fasted samples across all treatments. Supplementation of creatine, carnitine, and choline in grain-free diets may play a role in sparing the methionine requirement without increasing homocysteine concentrations. Supplementing these nutrients could also aid in the treatment of disease that causes metabolic or oxidative stress, including cardiac disease in dogs, but future research is required.

中文翻译：

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在无谷物饮食中添加膳食蛋氨酸而不是膳食牛磺酸或甲基供体/受体会增加成年犬的餐后同型半胱氨酸浓度

无谷物宠物食品中的豆类成分部分取代了谷物成分。豆类成分中蛋氨酸和半胱氨酸的含量较低，这是狗体内牛磺酸合成的氨基酸 (AA) 前体。尽管最近的工作已经研究了饲喂无谷物饮食时的血浆和全血牛磺酸浓度，但尚未评估在无谷物饮食中补充牛磺酸生物合成中涉及的各种营养素。本研究旨在调查在完全无谷物干狗粮中添加蛋氨酸 (MET)、牛磺酸 (TAU) 或甲基供体（胆碱）和甲基受体（肌酸和肉碱；CCC）对餐后 AA 浓度的影响。八只健康的比格犬被喂食三种治疗中的一种或对照无谷物饮食 (CON) 7 天，采用 4 × 4 拉丁方设计。第 7 天，放置头颅导管，并在 15、30、60、90、120、180、240、300 和 360 分钟收集一个空腹样本（0 分钟）和一系列 9 个餐后血样。使用 SAS（版本 9.4）中的 PROC GLIMMIX 函数将数据分析为重复测量。与喂食 CON 的狗相比，喂食 MET 的狗在餐后 30 至 360 分钟的血浆和全血蛋氨酸浓度更高（P < 0.0001），在餐后 60 至 360 分钟的血浆同型半胱氨酸浓度更高（P < 0.0001）， TAU 和 CCC。与喂食 CON 的狗相比（P = 0.02），喂食 TAU 的狗随着时间的推移具有更高的血浆牛磺酸浓度，但与喂食 MET 和 CCC 的狗没有差异（P > 0.05）。此外，与所有治疗的禁食样品相比，大多数 AA 在餐后 6 小时仍显着升高。补充肌酸，无谷物饮食中的肉碱和胆碱可能在不增加同型半胱氨酸浓度的情况下减少蛋氨酸需求。补充这些营养素还可以帮助治疗导致代谢或氧化应激的疾病，包括狗的心脏病，但需要未来的研究。