Abstract

High concentrate (HC) diet feeding leads to the lysis of rumen microbes and the release of hazardous metabolites, which can trigger inflammatory responses, thereby impairing dairy cow health and production. γ-D-glutamyl-meso-diaminopimelic acid (iE-DAP), which constitutes the peptidoglycan (PGN) layer of bacteria, is the minimum PGN structure capable of activating inflammatory signaling pathways. This research paper aimed to determine the iE-DAP concentration and investigate the effects of an HC diet on the concentration of iE-DAP in the rumen fluid of dairy cows. However, there are limited studies on the determination of iE-DAP concentration. Hence, we established a high-performance liquid chromatography (HPLC) method combined with pre-column chiral derivatization to detect the concentration of iE-DAP in rumen fluid. Moreover, we conducted an animal experiment that included 12 lactating Holstein cows, which were randomly divided into a low-concentrate (LC) group and an HC group. The results showed that the linear range of iE-DAP was 5–500 µg/mL and that the intra- and inter-day RSDs were lower than 7%. Meanwhile, this method was successfully applied to the analysis of iE-DAP in rumen fluid, and the results revealed that long-term feeding with an HC diet elevated the concentration of iE-DAP in rumen fluid of dairy cows.

摘要

高浓度 (HC) 日粮饲喂会导致瘤胃微生物裂解和有害代谢物的释放，从而引发炎症反应，从而损害奶牛的健康和生产。γ -D-谷氨酰-内消旋-二氨基庚二酸 (iE-DAP) 构成细菌的肽聚糖 (PGN) 层，是能够激活炎症信号通路的最小 PGN 结构。本研究论文旨在确定 iE-DAP 浓度并研究 HC 日粮对奶牛瘤胃液中 iE-DAP 浓度的影响。然而，关于iE-DAP浓度测定的研究有限。因此，我们建立了一种高效液相色谱法（HPLC）结合柱前手性衍生化检测瘤胃液中iE-DAP浓度的方法。此外，我们进行了一项动物实验，包括 12 头泌乳荷斯坦奶牛，它们被随机分为低浓度 (LC) 组和 HC 组。结果表明，iE-DAP 的线性范围为 5–500 µg/mL，日内和日间 RSD 均低于 7%。同时，将该方法成功应用于瘤胃液中iE-DAP的分析，结果表明，长期饲喂HC日粮会提高奶牛瘤胃液中iE-DAP的浓度。