Context Determination of the neutral detergent fibre digestibility is one of the important parameters to consider when formulating diets. However, the in vitro determination shows low repeatability because of the source of rumen-fluid inoculum. Priming of the rumen fluid inocula, obtained through an oesophageal probe, has been proposed to overcome this issue. Aim The objective of the study was to investigate the evolution of the microbial enzymatic activities of different rumen fluids during a priming procedure, to establish the fermentation interval that minimises the differences among rumen-fluid degradative potentials. Methods Three farms for each type of diet were involved in the study. Rumen fluids were obtained from dry and lactating cows fed the following four diet types: 100% hay or a diet with 80 : 20 forage : concentrate ratio (F : C) as dry-cow diets, and ad libitum hay and concentrate, or a total mixed ration (both at 60 : 40 F : C) as lactating-cow diets. On each farm, rumen fluid was collected from three Holstein cows by using an oesophageal probe, and mixed. Two aliquots of each rumen fluid mix were added to the medium containing the same priming substrate in an in vitro batch-fermentation system. During the incubation, the fermentation fluids were sampled in duplicate at 0-, 1-, 2-, 4-, 8-, 24- and 48-h intervals. Enzymatic activities of amylase, cellulase and xylanase were determined by radial enzyme diffusion method. Key results Initial enzymatic activities were quite variable and increased with an increasing incubation time. By 24 h, amylase showed similar values among high-concentrate diet fermentation fluids, and a lower data dispersion in comparison to the other intervals; cellulase was characterised by similar values in all the fermentation fluids derived from diets including concentrates, and xylanase showed similar activity in the fermentation fluids derived from high-concentrate diets. Development of the enzymatic activity of the fermentation fluids derived from the 100% hay diet differed from the others. Conclusions A 24-h priming procedure was needed to stabilise and equalise the enzymatic activity of the rumen fluid from cows fed high-concentrate diets. This was not observed in rumen fluid from cows fed hay-based diets. Implications The 24-h-primed rumen fluid can be used to increase the repeatability of neutral detergent fibre digestibility determination.

中文翻译：

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通过径向酶扩散法确定体外消化率试验中用作接种物的瘤胃液的最佳引发间隔

背景 中性洗涤纤维消化率的测定是配制日粮时要考虑的重要参数之一。然而，由于瘤胃液接种物的来源，体外测定显示出低重复性。已经提议对通过食道探针获得的瘤胃液接种物进行灌注以克服这个问题。目的 本研究的目的是调查不同瘤胃液在启动过程中微生物酶活性的演变，以确定发酵间隔，最大限度地减少瘤胃液降解潜力之间的差异。方法 每种饮食类型的三个农场参与了这项研究。瘤胃液来自饲喂以下四种日粮类型的干奶牛和泌乳奶牛：100% 干草或饲草：精料比例为 80:20 的日粮（F : C) 作为干奶牛日粮，随意采食干草和浓缩物，或作为泌乳奶牛日粮的总混合日粮（均在 60 : 40 F : C）。在每个农场，使用食管探针从三头荷斯坦奶牛收集瘤胃液并混合。在体外分批发酵系统中，将每种瘤胃流体混合物的两份等分试样添加到含有相同引发底物的培养基中。在培养过程中，发酵液以 0、1、2、4、8、24 和 48 小时的间隔一式两份取样。采用径向酶扩散法测定淀粉酶、纤维素酶和木聚糖酶的酶活性。主要结果 初始酶活性变化很大，并且随着孵育时间的增加而增加。到 24 小时，淀粉酶在高浓度日粮发酵液中显示出相似的值，与其他区间相比，数据分散性较低；纤维素酶在源自包括浓缩物的饮食的所有发酵液中的特征在于相似的值，并且木聚糖酶在源自高浓缩饮食的发酵液中显示出相似的活性。源自 100% 干草饮食的发酵液的酶活性的发展与其他发酵液不同。结论 需要一个 24 小时的启动程序来稳定和均衡饲喂高浓度日粮的奶牛瘤胃液的酶活性。这在饲喂以干草为基础的饮食的奶牛的瘤胃液中没有观察到。含义 24 小时预浸的瘤胃液可用于提高中性洗涤纤维消化率测定的可重复性。纤维素酶在源自包括浓缩物的饮食的所有发酵液中的特征在于相似的值，并且木聚糖酶在源自高浓缩饮食的发酵液中显示出相似的活性。源自 100% 干草饮食的发酵液的酶活性的发展与其他发酵液不同。结论 需要一个 24 小时的启动程序来稳定和均衡饲喂高浓度日粮的奶牛瘤胃液的酶活性。这在饲喂以干草为基础的饮食的奶牛的瘤胃液中没有观察到。含义 24 小时预浸的瘤胃液可用于提高中性洗涤纤维消化率测定的可重复性。纤维素酶在源自包括浓缩物的饮食的所有发酵液中的特征在于相似的值，并且木聚糖酶在源自高浓缩饮食的发酵液中显示出相似的活性。源自 100% 干草饮食的发酵液的酶活性的发展与其他发酵液不同。结论 需要一个 24 小时的启动程序来稳定和均衡饲喂高浓度日粮的奶牛瘤胃液的酶活性。这在饲喂以干草为基础的饮食的奶牛的瘤胃液中没有观察到。含义 24 小时预浸的瘤胃液可用于提高中性洗涤纤维消化率测定的可重复性。源自 100% 干草饮食的发酵液的酶活性的发展与其他发酵液不同。结论 需要一个 24 小时的启动程序来稳定和均衡饲喂高浓度日粮的奶牛瘤胃液的酶活性。这在饲喂以干草为基础的饮食的奶牛的瘤胃液中没有观察到。含义 24 小时预浸的瘤胃液可用于提高中性洗涤纤维消化率测定的可重复性。源自 100% 干草饮食的发酵液的酶活性的发展与其他发酵液不同。结论 需要一个 24 小时的启动程序来稳定和均衡饲喂高浓度日粮的奶牛瘤胃液的酶活性。这在饲喂以干草为基础的饮食的奶牛的瘤胃液中没有观察到。含义 24 小时预浸的瘤胃液可用于提高中性洗涤纤维消化率测定的可重复性。