Global warming has turned as a global concern for especially those who engaged in animal agriculture. The use of non-conventional feedstuff (e.g., plants and plant extracts) has also become an interesting topic since they are natural products, environmentally friendly and safe in food production. These potential feed additives are rich sources of secondary compounds. The ideal effects of these plant secondary compounds on ruminant would be to reduce methane (CH 4 ) production with no negative effect on rumen fermentation characteristics. The aim of the present review was to summarize the related studies from published papers in recent years. Based on published data, plants and plant extracts of various origins have shown to inhibit ruminal CH 4 production (methanogenesis) when fed to ruminants either as forages or as extracts tested in vitro or in vivo. The suppressed methanogenesis was mostly attributed to improving fermentation characteristics (e.g., increase in propionic concentration) as well as antimethanogenic and antiprotozoal activities of these feedstuff. However, it should be noted that the effectiveness of these feed additives depends on the source, type and level at which they are being used. In conclusion, plants and plant extracts seem promising as feed supplements for ruminant nutrition.

中文翻译：

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参考瘤胃产甲烷将植物副产品用作牲畜饲养的非常规饲料

全球变暖已成为全球关注的问题，尤其是那些从事畜牧业的人。非常规饲料（例如植物和植物提取物）的使用也已成为一个有趣的话题，因为它们是天然产品，在食品生产中对环境友好且安全。这些潜在的饲料添加剂是次要化合物的丰富来源。这些植物次生化合物对反刍动物的理想作用是减少甲烷 (CH 4 ) 产生，而对瘤胃发酵特性没有负面影响。本综述的目的是总结近年来发表论文的相关研究。根据公布的数据，各种来源的植物和植物提取物在作为饲草或体外或体内测试的提取物饲喂给反刍动物时已显示抑制瘤胃 CH 4 的产生（产甲烷）。抑制的产甲烷作用主要归因于发酵特性的改善（例如丙酸浓度的增加）以及这些饲料的抗甲烷生成和抗原生动物活性。然而，应该注意的是，这些饲料添加剂的有效性取决于它们的来源、类型和使用水平。总之，植物和植物提取物作为反刍动物营养的饲料补充剂似乎很有前景。丙酸浓度的增加）以及这些饲料的抗甲烷和抗原生动物活性。然而，应该注意的是，这些饲料添加剂的有效性取决于它们的来源、类型和使用水平。总之，植物和植物提取物作为反刍动物营养的饲料补充剂似乎很有前景。丙酸浓度的增加）以及这些饲料的抗甲烷和抗原生动物活性。然而，应该注意的是，这些饲料添加剂的有效性取决于它们的来源、类型和使用水平。总之，植物和植物提取物作为反刍动物营养的饲料补充剂似乎很有前景。