Identification of bioactive grassland plants for reducing enteric methane production and rumen proteolysis using an in vitro screening assay

Abstract

The aim of this study was to conduct in vitro rumen fermentation assays on a large number of grassland plants to discriminate them on the basis of their potential to combine high nutritive value for ruminants and a reduced impact on the environment. In total, 156 plant species collected from diversified grasslands in the French Massif Central were screened by measuring several parameters, including in vitro true organic matter digestibility (IVTOMD), methane (CH4) production and ammonia nitrogen (N-NH3) in the incubation medium as an indicator of dietary protein degradation in the rumen. The results were expressed relative to perennial ryegrass (PRG) values used as a reference. We observed that the fermentation of 13 plants produced 50% less CH4 per unit of OM truly digested than did fermentation of PRG. Among these plants, two (Bidens tripartita subsp. Tripartite and Scrophularia nodosa) reduced CH4 by more than 80%. In terms of protein degradation, the fermentation of 37 plants halved the ratio between N-NH3 and plant N content compared with PRG, of which six had values below the detection level of the assay. Interestingly, 16 plants showed simultaneously a reduction of more than 80% in N-NH3 production and 30% in CH4 production, including three plants (Sedum telephium subsp. maximum, Oenothera biennis and Geranium sylvaticum) with an IVTOMD higher than 80%. This study has provided more knowledge about the use of lesser-known plants as whole plant forage by ruminants, and has identified candidate plants for potential use as additives in the form of plant extracts.