Effects of Condensed Tannins in <i>Polygonum viviparum</i> Leaves on In Vitro Rumen Fermentation and Methane Emissions

Condensed tannins (CT) in forages can effectively reduce methane emissions from ruminants, but the relationship between CT properties and antimethanogenic activity of CT in the rumen has not been clearly elucidated. This study aimed to probe the effects of CT content and structures on rumen fermentation and methane emissions. The chemical properties of CT in Polygonum viviparum leaves were characterised. An in vitro fermentation experiment was conducted to determine gas and methane production, fermentation parameters and volatile fatty acid concentrations by the in vitro gas production technology. P. viviparum leaves contained a high level of CT (117.2–181.4 g kg −1 DM), which decreased total gas production, methane production, ammonia content and volatile fatty acid concentrations by 4.60%–29.62%, 5.38%–33.23%, 33.70%–39.50% and 9.76%–22.06%, respectively. The prodelphinidin: procyanidin monomer ratio in the present study is the main responsible factor explaining the methane reduction in the CT structures. P. viviparum , especially its leaves with superior nutritional quality at the vegetative stage, can be used as a feed supplement to improve rumen fermentation and reduce methane production. This study will help to utilise tannin‐rich native forages, promote the sustainable development of animal husbandry and contribute to the mitigation of global climate change.