Phenolic compounds and forage quality affect methane production potential from Swiss alpine summer pastures

Summary in the original language of the document

Alpine summer pastures are of high biodiversity and cultural value, but tend to provide forage of higher fibre content and lesser digestibility than more intensively managed grassland. This, in turn, may lead to higher enteric methane emissions from ruminants grazing these pastures. On the other hand, the diverse vegetation may be rich in tannins and other phenolics that can decrease enteric methane emissions. To investigate these relationship, we took botanical relevés and sampled first-growth herbage from a total of 45 alpine summer pastures in two years. These pastures represented nutrient-poor and nutrient-rich sites at different altitudes in regions spread across the Swiss Alps. We determined concentrations of neutral detergent fibre (NDF), total phenolics (TEP), total tannins (TT) and condensed tannins (CT) and assessed in-vitro methanogenesis using the Hohenheim Gas Test. Concentrations of all phenolics fractions varied greatly between sites and were negatively correlated with NDF. With increasing NDF concentrations, total methane production decreased but methane production per ml gas increased. By contrast, increasing concentrations of TEP, TT and CT led to decreases in both total methane production an methane production per ml gas. Our results indicate that phenolics in the herbage of alpine summer pastures may help to reduce the methane production potential of the ruminants taht graze there.