Observed improvements in animal and sward performance, coupled with a desire for more sustainable pasture-based feeding systems, has triggered a surge in the implementation of more botanically diverse pastures. However, thus far, there has been limited research investigating the effects of botanically diverse sward types on enteric methane (CH4) or nitrogen (N) excretion, alongside the ruminal microbiota and fermentation profile, in sheep. Hence, this study investigates the effect of sward type on CH4 production and N excretion, in addition to assessing the rumen microbiome, volatile fatty acid proportions, and ammonia nitrogen (NH3-N) concentration in sheep. A 5 × 5 Latin square design experiment was implemented to investigate 5 dietary treatments; perennial ryegrass (Lolium perenne L.; PRG) only or PRG plus white clover (Trifolium repens L.; PRG + WC), red clover (Trifolium pratense L.; PRG + RC), chicory (Chicorium intybus L.; PRG + Chic) or plantain (Plantago lanceolata L.; PRG + Plan). Diets were mixed at a ratio of 75% PRG and 25% of the respective companion forage and 100% PRG for the PRG treatment, on a dry matter basis. Twenty castrated male sheep were housed in metabolism crates across 5 feeding periods. Methane measurements were acquired utilizing portable accumulation chambers. Rumen fluid was harvested using a transoesophageal sampling device. Microbial rumen DNA was extracted and subjected to 16S rRNA amplicon sequencing and fermentation analysis. Data were analyzed using PROC MIXED in SAS. Results show that animals consuming PRG + WC ranked lower for CH4 production (g/d) than sheep offered PRG, PRG + Chic or PRG + Plan (P < 0.01) while the addition of any companion forage ranked CH4 yield (g/kg dry matter intake (DMI)) lower (P < 0.001) than PRG. There was a moderate positive correlation between DMI and CH4 (g/d; r = 0.51). Ruminal NH3-N was lowest in animals consuming the PRG diet (P < 0.01). There was a greater abundance of Methanobrevibacter and reduced abundance of Methanosphaera (P < 0.001) in sheep offered PRG, compared with any binary sward. On average, herb diets (PRG + Chic or PRG + Plan) reduced the urinary nitrogen concentration of sheep by 34% in comparison to legume diets (PRG + WC or PRG + RC) and 13% relative to the PRG diet (P < 0.001). Sheep offered PRG + Chic had a greater dietary nitrogen use efficiency than PRG + RC (P < 0.05). This study demonstrates the potential for sward type to influence rumen function and the microbial community, along with CH4 and N output from sheep.

中文翻译：

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Sward 型改变了绵羊肠道甲烷排放、氮输出和瘤胃微生物生态系统的相对丰度


观察到的动物和草地性能的改善，加上对更可持续的基于牧场的饲喂系统的渴望，引发了更多植物多样化牧场的实施激增。然而，到目前为止，调查植物学上不同的草地类型对绵羊肠道甲烷 （CH4） 或氮 （N） 排泄以及瘤胃微生物群和发酵特征的影响的研究有限。因此，本研究除了评估绵羊瘤胃微生物组、挥发性脂肪酸比例和氨氮 （NH3-N） 浓度外，还调查了 sward 型对 CH4 产生和 N 排泄的影响。实施 5 × 5 拉丁方格设计实验，研究 5 种饮食处理;多年生黑麦草 （Lolium perenne L.;PRG） 或 PRG 加白三叶草 （Trifolium repens L.;PRG + WC）、红三叶草 （Trifolium pratense L.;PRG + RC）、菊苣 （Chicorium intybus L.;PRG + Chic）或车前草（Plantago lanceolata L.;PRG + Plan） 的 PRG + Plan）。以干物质为基础，以 75% PRG 和 25% 各自伴生牧草和 100% PRG 的比例混合日粮用于 PRG 处理。20 只被阉割的雄性绵羊被饲养在 5 个饲喂期的新陈代谢箱中。使用便携式蓄积室进行甲烷测量。使用经食管取样装置收集瘤胃液。提取微生物瘤胃 DNA，进行 16S rRNA 扩增子测序和发酵分析。在 SAS 中使用 PROC MIXED 分析数据。结果表明，食用 PRG + WC 的动物的 CH4 产量 （g/d） 低于提供 PRG、PRG + Chic 或 PRG + Plan 的绵羊 （P < 0.01），而添加任何伴侣饲料的 CH4 产量 （g/kg 干物质摄入量 （DMI）） 低于 PRG （P < 0.001）。 DMI 和 CH4 之间存在中度正相关 （g/d;r = 0.51）。食用 PRG 饮食的动物瘤胃 NH3-N 最低 （P < 0.01）。与任何二元饲养相比，提供 PRG 的绵羊中 Methanobrevibacter 的丰度更高，而 Methanosphaera 的丰度更低 （P < 0.001）。平均而言，与豆类饮食（PRG + WC 或 PRG + RC）相比，草本饮食（PRG + Chic 或 PRG + Plan）使绵羊的尿氮浓度降低了 34%，相对于 PRG 饮食降低了 13%（P < 0.001）。提供 PRG + Chic 的绵羊比 PRG + RC 具有更高的日粮氮利用效率 （P < 0.05）。这项研究表明，草地型可能影响瘤胃功能和微生物群落，以及绵羊的 CH4 和 N 输出。