This study assessed relative bioavailability of guanidinoacetic acid (GAA) in cattle. Seven ruminally cannulated Holstein steers (initial body weight of 280 kg) were used in an experiment with a 5 × 5 Latin square design; the 2 additional steers received a treatment sequence identical to 2 steers in the Latin square. Treatments were: control (no GAA, water infusion), ruminal infusion of 10 or 20 g/d GAA, and abomasal infusion of 10 or 20 g/d GAA, with all infusions delivered continuously. Periods were 7 d in length, and on d 7 blood and urine samples were collected to determine concentrations of GAA and its associated metabolites. Plasma creatine concentrations increased linearly (P < 0.01) with GAA infusion to the abomasum and tended to increase linearly (P = 0.06) when GAA was infused ruminally. Urinary creatine concentrations increased linearly with increasing amounts of GAA infused in the abomasum (P < 0.01) and the rumen (P < 0.05). There were no significant effects of GAA infusion to either the abomasum or rumen on plasma or urinary concentrations of GAA. Plasma creatinine concentrations were not affected by GAA infusion to the abomasum or rumen. Urinary creatinine concentrations decreased when GAA was infused abomasally (P < 0.05). Because plasma and urinary creatine concentrations yielded the statistically strongest linear responses, they were selected as the primary response criteria for quantifying ruminal escape of GAA. Calculated by slope-ratio methodology, estimates for ruminal escape of GAA based on plasma creatine and urinary creatine concentrations were 47% and 49%, respectively. Ruminally infused GAA was about half as effective as abomasally infused GAA in elevating plasma and urinary concentrations of creatine.

中文翻译：

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以瘤胃或真胃方式输送给牛的胍基乙酸的相对生物利用度。

本研究评估了牛体内胍基乙酸 (GAA) 的相对生物利用度。7 头瘤胃插管荷斯坦公牛（初始体重 280 公斤）用于 5 × 5 拉丁方设计的实验；额外的 2 头公牛接受了与拉丁广场中的 2 头公牛相同的治疗顺序。处理为：对照（无 GAA，水输注）、10 或 20 g/d GAA 的瘤胃输注和 10 或 20 g/d GAA 的皱胃输注，所有输注均连续输送。周期为 7 天，在第 7 天收集血液和尿液样本以确定 GAA 及其相关代谢物的浓度。血浆肌酸浓度随着 GAA 输注至真胃呈线性增加（P < 0.01），并趋于线性增加（P= 0.06) 当在瘤胃中注入 GAA 时。尿肌酸浓度随GAA的量线性增加输注在皱胃（P <0.01）和瘤胃（P <0.05）。GAA 输注到真胃或瘤胃对血浆或尿 GAA 浓度没有显着影响。血浆肌酐浓度不受 GAA 注入真胃或瘤胃的影响。当 GAA 被皱缩注入时，尿肌酐浓度降低（P< 0.05)。因为血浆和尿肌酸浓度产生了统计上最强的线性反应，所以它们被选为量化瘤胃逃逸 GAA 的主要反应标准。通过斜率比方法计算，基于血浆肌酸和尿肌酸浓度的 GAA 瘤胃逃逸估计值分别为 47% 和 49%。在提高血浆和尿肌酸浓度方面，瘤胃注入 GAA 的效果大约是皱胃注入 GAA 的一半。