Instituto de Ganadería de Montaña (CSIC-ULE), Finca Marzanas s/n, 24346 Grulleros, León, Spain.
Animal. 2013 Jun;7(6):940-7. doi: 10.1017/S1751731112002455. Epub 2013 Jan 8.
Oxalic acid (OA) is a secondary compound occurring in a wide range of plants consumed by ruminants, especially in saline lands or in arid and semi-arid regions. However, its impact on the rumen microbial community and its changes over time, as well as the potential consequences on ruminal function, remain unknown. To examine this impact, five ewes fitted with a ruminal cannula and fed low-quality grass hay were dosed daily with 0.6 mmol of OA/kg body weight through the cannula for 14 days. On days 0 (before the start), 4, 7 and 14 of the administration period, samples of ruminal digesta were collected throughout the day (0, 3, 6 and 9 h after the morning feeding) for analysis of the bacterial community and fermentation parameters (pH, ammonia and volatile fatty acid (VFA) concentrations). In addition, two feedstuffs were incubated in situ using the nylon bag technique to estimate ruminal degradation. Terminal restriction fragment length polymorphism was employed to monitor the dynamics of total bacteria, and quantitative real-time PCR was used to investigate the abundance of the oxalate-degrading Oxalobacter formigenes. Neither pH nor total VFA concentrations were affected. Nevertheless, OA dosing altered molar proportions of most individual VFA and ammonia concentrations (P < 0.001). The dry matter disappearance of alfalfa hay was reduced on days 7 and 14 and that of barley straw only on day 7 (P < 0.01). These slight changes were related to others observed in the relative frequency of a number of terminal restriction fragments. Variations in the ruminal microbiota occurred rapidly with OA administration, which did not modify the bacterial diversity significantly but altered the structure of the community. However, many of these changes were reversed by the end of the experiment, with no significant differences between days 0 and 14 of dosing. These results suggest a rapid adaptation of the rumen bacterial community linked to the estimated increase in the abundance of O. formigenes (from 0.002% to 0.007% of oxc gene in relation to the total bacteria 16S rDNA; P < 0.01), which is assumed to be responsible for oxalate breakdown.
草酸（OA）是一种次生化合物，存在于反刍动物食用的广泛植物中，特别是在盐碱地或干旱和半干旱地区。然而，其对瘤胃微生物群落的影响及其随时间的变化，以及对瘤胃功能的潜在影响尚不清楚。为了研究这种影响，给五只瘘管羊每天通过瘘管灌服 0.6mmol/kg 体重的 OA，持续 14 天。在给药期的第 0 天（开始前）、第 4 天、第 7 天和第 14 天，全天（上午喂食后 0、3、6 和 9 小时）收集瘤胃液样本，用于分析细菌群落和发酵参数（pH 值、氨和挥发性脂肪酸（VFA）浓度）。此外，使用尼龙袋技术原位孵育两种饲料，以估计瘤胃降解率。末端限制性片段长度多态性用于监测总细菌的动态，定量实时 PCR 用于研究草酸降解菌 Oxalobacter formigenes 的丰度。pH 值和总 VFA 浓度均未受影响。然而，OA 给药改变了大多数单个 VFA 的摩尔比例和氨浓度（P < 0.001）。苜蓿干草的干物质消失率在第 7 天和第 14 天降低，而大麦秸秆仅在第 7 天降低（P < 0.01）。这些微小的变化与一些末端限制性片段的相对频率观察到的其他变化有关。随着 OA 给药，瘤胃微生物群迅速发生变化，这并没有显著改变细菌多样性，但改变了群落的结构。然而，这些变化中的许多在实验结束时得到了逆转，在给药的第 0 天和第 14 天之间没有显著差异。这些结果表明，与估计的 Oxalobacter formigenes 丰度增加相关的瘤胃细菌群落的快速适应（与 16S rDNA 总细菌相比，oxc 基因的丰度从 0.002%增加到 0.007%；P < 0.01），这被认为是负责草酸分解。
