Context: High concentrations of crude protein in ruminant diets may lead to excessive production of ruminal ammonia, which may stress the animal’s metabolism and impact nitrogen efficiency. This may become a problem in zero-concentrate feeding systems when pasture grass is rich in crude protein. Polyphenols such as tannins may protect part of dietary protein from ruminal degradation and thus inhibit ammonia formation. Aims: The present study screened mature herbs for their potential to mitigate ruminal ammonia formation in cattle, when provided as a supplement to a forage diet. Methods: Thirty-five temperate-climate, herbaceous meadow plant species (including three legumes) that appear in biodiverse natural and sown pastures were investigated for their effects on ruminal ammonia production. Aboveground material was harvested during ripening of the seeds and analysed for nutrient and phenol concentrations. Net energy and protein absorbable at the duodenum were calculated. Incubations (24 h) with cattle rumen fluid following the in vitro Hohenheim Gas Test protocol were performed to compare the effects of the test plants on ruminal gas and ammonia formation. Test plants replaced one-third of a basal mixture consisting of 57% Lolium perenne L. and 43% Medicago sativa L. (air-dry-matter basis). Results were compared with those obtained with the basal mixture alone. Key results: According to regression analysis, ammonia concentration after incubation was negatively related to concentrations of total extractable phenols and total tannins in feed mixtures, whereas the relationship was weakly positive with dietary crude protein. In 23 and 19 of the test diets, respectively, in vitro gas production (indicating ruminal organic matter digestibility) and ammonia concentrations in the incubation medium after 24 h were significantly lower than with the basal mixture alone. Incubations containing Galium verum L., Leontodon hispidus L., Lotus corniculatus L., Onobrychis viciifolia Scop., Plantago lanceolata L., Sanguisorba minor Scop. and Scabiosa columbaria L. maintained gas production and estimated in vitro organic matter digestibility while at the same time lowering ammonia concentrations. Conclusions: Seven mature herbs of a screening of 35 proved to have potential for positive effects on ruminal protein utilisation without impairing fermentation. Implications: These herbs are of particular interest as dietary supplements for dairy cows grazing protein-rich pastures.

中文翻译：

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作为反刍动物饲料补充剂的成熟草药：对体外瘤胃发酵和氨生成的影响

背景：反刍动物日粮中高浓度的粗蛋白可能导致瘤胃氨的过量产生，这可能会影响动物的新陈代谢并影响氮效率。当牧草富含粗蛋白时，这可能成为零浓度饲喂系统中的一个问题。多酚如单宁可以保护部分日粮蛋白质免于瘤胃降解，从而抑制氨的形成。目的：本研究筛选了成熟的草本植物，当它们作为草料日粮的补充剂提供时，它们有可能减轻牛的瘤胃氨形成。方法：研究了出现在具有生物多样性的天然和播种牧场中的 35 种温带气候、草本草甸植物物种（包括三种豆科植物）对瘤胃氨生成的影响。在种子成熟期间收获地上材料并分析养分和苯酚浓度。计算在十二指肠可吸收的净能量和蛋白质。按照体外霍恩海姆气体测试方案，用牛瘤胃液进行孵育（24 小时），以比较测试植物对瘤胃气体和氨形成的影响。测试植物替换了由 57% 多年生黑麦草和 43% 苜蓿（风干物质基础）组成的基础混合物的三分之一。结果与单独使用基础混合物获得的结果进行了比较。主要结果：根据回归分析，孵化后的氨浓度与饲料混合物中总可提取酚和总单宁的浓度呈负相关，而与日粮粗蛋白呈弱正相关。分别在 23 和 19 种测试日粮中，24 小时后体外产气量（表明瘤胃有机物消化率）和孵化培养基中的氨浓度显着低于单独的基础混合物。包含 Galium v​​erum L.、Leontodon hispidus L.、Lotuscorniculatus L.、Onobrychis viciifolia Scop.、Plantago lanceolata L.、Sanguisorba minor Scop. 的孵化。和 Scabiosa columbaria L. 维持气体产量并估计体外有机物消化率，同时降低氨浓度。结论：从 35 种筛选中筛选出的 7 种成熟草药被证明对瘤胃蛋白质利用具有积极影响而不影响发酵。含义：这些草药作为在富含蛋白质的牧场放牧的奶牛的膳食补充剂特别令人感兴趣。