Potential and Limitations of plant polyphenols to reduce methane emissions from ruminants in grassland systems

• Applicant: Professor Dr. Friedhelm Taube, since 1/2022
• Subject Area: Plant Cultivation, Plant Nutrition, Agricultural Technology ; Plant Biochemistry and Biophysics
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 406534244

Methane emissions from ruminant agriculture account for 12-17% of all EU-27 GHG emissions. However, possibilities to reduce these emissions are limited in Europe without risking decrements in the animal’s productivity. One of the few existing possibilities is the feeding of forage plants that contain tannins. Although research on this topic has been conducted for several years already, results about the potential of forage species to reduce methane emissions were highly variable. This prevented a widespread application of tannin-containing forage plants in agriculture, despite the beneficial side effect of increasing grassland biodiversity. One of the main reasons for the observed variability in antimethanogenic potential is that previous experiments usually only quantified total phenolic compounds. This is problematic as it ignores the structural characteristics of tannins, which have been proven to affect the bioactivity substantially. Additionally, only very few species were analysed and also in pool samples rather than individual plants, hence ignoring the variability within species and making previous results even more difficult to interpret. Nevertheless, recent advances in the analysis of tannins permitted faster and better analyses of both tannin concentration and their structural characteristics. Additionally, these new methods permit a simultaneous quantification of flavonoids or other polyphenols with potential bioactivity that might be present in the forage species as well.We put forward the following hypotheses: i) an accurate and improved characterisation of tannins will permit an improved assessment of their antimethanogenic potential, ii) the effect of these tannins can be reduced or increased, dependent on the co-presence of additional polyphenols, and iii) differences in growing conditions have affected the tannin content in previous studies, thus making comparisons among these studies difficult. To solve these issues, we will cultivate different individuals of several cultivars from eight tannin containing forage species under identical environmental conditions, and subsequently analyse their bioactive compounds with the most modern equipment available. Furthermore, their methane reducing potential will be quantified using the Hohenheim gas test. The experimental design for this experiment was optimized for the statistical analysis of the link between the chemical characterization and the observed bioactivity, and to permit extrapolation of results to additional species. Finally, in this experiment, we will analyse protein and fibre bound tannins for the first time, as they might contribute to the ant-methanogenic effect. Hence, this study provides an excellent basis for subsequent in vivo trials.This research project benefits from the experience of the group members in phytochemical analyses, as well as regarding forage production, grassland systems and animal nutrition.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Dr. Carsten Malisch, until 12/2021