Diversity of condensed tannin structures affects rumen in vitro methane production in sainfoin ( Onobrychis viciifolia ) accessions

Sainfoin is a non‐bloating temperate forage legume with a moderate‐to‐high condensed tannin ( CT ) content. This study investigated whether the diversity of sainfoin accessions in terms of CT structures and contents could be related to rumen in vitro gas and methane ( CH 4 ) production and fermentation characteristics. The aim was to identify promising accessions for future investigations. Accessions differed ( P  < 0·0001) in terms of total gas and CH 4 productions. Fermentation kinetics (i.e. parameters describing the shape of the gas production curve and half‐time gas production) for CH 4 production were influenced by accession ( P  ≤ 0·038), but not by PEG . Accession, PEG and time affected ( P  < 0·001) CH 4 production, but accession and PEG interaction showed only a tendency ( P  = 0·08). Increase in CH 4 due to PEG addition was not related to CT content. Further analysis of the relationships among multiple traits (nutritional composition, CT structure and CH 4 production) using principal component analysis ( PCA ) based on optimally weighted variables revealed differences among accessions. The first two principal component axes, PC 1 (57·6%) and PC 2 (18·4%), explained 76·0% of the total variation among accessions. Loading of biplots derived from both PCA s made it possible to establish a relationship between the ratio of prodelphinidin:procyanidin ( PD : PC ) tannins and CH 4 production in some accessions. The PD : PC ratio seems to be an important source of variation that is negatively related to CH 4 production. These results suggested that sainfoin accessions collected from across the world exhibited substantial variation in terms of their effects on rumen in vitro CH 4 production, revealing some promising accessions for future investigations.