Alpine pasture plant species affect in vitro rumen methane production and kinetics

This study aimed to evaluate the influence of different plant species widespread in alpine pastures on in vitro rumen fermentation parameters and methane kinetic production. A total of 11 plant species were sampled at the beginning of the grazing season and used as substrates in an in vitro batch fermentation system. After 24h of fermentation, plants affected volatile fatty acids profiles, ammonia yield, and dry matter (DM) digestibilities. Carum carvi, Ranunculus. acris and Festuca rubra showed the highest total production of methane per unit of digested DM while Potentilla erecta was the species that produced less methane. In terms of methane as a percentage of the total gas, F. rubra had the highest value (28.9%) while R. acris had the lowest (24.2%). Total gas and methane production were monitored continuously and the percentage of methane in total gas was fitted with the Gompertz model. Plants differed significantly (p < .01) in methane production kinetics, including production rate decline (A), asymptotic methane concentration (B), time to maximum fermentation rate (TMFR), and maximum fermentation rate (MFR). C. carvi, Prunella grandiflora, and R. acris showed high values of MFR and the top values in the production rate decline (A > 0.9). The two grasses (F. rubra and Poa alpina) together with Hypericum maculatum showed an opposite behaviour with low values in MFR, A and a longer TMFR. The results of the methane production kinetics allow for an in-depth evaluation of plant species, adding further information to those registered at the end of fermentation.