Screening of plants from diversified natural grasslands for their potential to combine high digestibility, and low methane and ammonia production

Abstract

A total of 156 plant species from 35 botanical families collected from diversified grasslands in the French Massif Central were screened in vitro for their potential to combine high nutritive value for ruminants and a reduced impact on the environment. The vegetative part of plants were analyzed for their chemical composition and incubated in a batch system containing buffered rumen fluid at 39°C for 24 h. The gas production and composition were recorded, and the fermentation end-product concentrations in the incubation medium and the in vitro true organic matter digestibility (IVTOMD) were determined. The results were expressed relative to perennial ryegrass (PRG) values used as a reference. We observed that no relationship between methane (CH 4 ) and volatile fatty acids (VFA) was evidenced for 12 plants, the fermentation of these plants producing significantly less CH 4 for a similar level of VFA production. In all, 13 plants showed 50% less CH 4 production per unit of organic matter truly digested (OMTD) than PRG. Among these plants, two reduced CH 4 by more than 80% and four species had an IVTOMD higher than 80%. The underlying modes of action seem to be different among plants: some result in an accumulation of H 2 in the fermentation gas, but others do not. In terms of nitrogen (N) use efficiency, the fermentation of 37 plants halved the ratio between ammonia (N-NH 3 ) and plant N content compared with PRG, of which six showed a complete absence of N-NH 3 in the medium. Among these plants, four maintained the IVTDMO at values not significantly different from PRG (P > 0.05). Considering the multi-criteria selection, 16 plants showed simultaneously a reduction of more than 80% in N-NH 3 production and 30% in CH 4 emission per unit of OMTD compared with PRG, including three with an IVTOMD higher than 80%. Overall, the botanical families that reduced simultaneously CH 4 and N-NH 3 most efficiently were the Rosaceae, Onagraceae, Polygonaceae and Dipsacaceae. The Onagraceae also gave high values for IVTOMD.

Methanogenic potential of forages consumed throughout the year by cattle in a Sahelian pastoral area

“…In the present study, NDF concentration seems to have a much greater effect on CH 4 production than does NDF digestibility; this results in the absence of seasonal differences in CH 4 production per gram NDF. Possibly, the discrepancy between the present study and that of Gemeda and Hassen (2014), on one hand, and those of Baccouche et al (2014) and Macheboeuf et al (2014), on the other hand, could be due to the presence of a majority of grasses ('straw' being mainly composed of grasses) and to the higher NDF concentration in the former two studies. Despite the higher CH 4 production per gram DM in the dry season, the very low intake that was simultaneously observed will certainly result in a lower emissions per animal, although CH 4 emission rate for a same diet is lower at low intakes (Chaokaur et al 2015, for Brahman zebus in the tropics).…”

“…Our results also showed a strong relationship between CH 4 production per gram DM and NDF concentration. This result agrees with results of Gemeda and Hassen (2014) who studied 16 grass species in the arid region of Kalahari with comparable climatic conditions, but not with those observed by Baccouche et al (2014) who performed in vitro incubations of 83 forages, of which 35 were grasses and legumes, harvested in the Ferlo region as in the present study, or those by Macheboeuf et al (2014) who studied 156 temperate plants, of which only one was grass and 13 were legumes. Our results are especially surprising because CH 4 production from forages depend both on their NDF concentration and on their digestibility, which are the two main drivers of hydrogen production from carbohydrate fermentation (Archimède et al 2011).…”

“…This decoupling between the VFA concentration (and thus production) and CH 4 production was already observed by Bodas et al (2008) who incubated 450 temperate plants, of which a small proportion had an antimethanogenic effect, by Meale et al (2012) for Australian and Ghanean grasses and leguminous shrubs, and by Baccouche et al (2014) with herbaceous species, but not with ligneous species. Conversely, Macheboeuf et al (2014) found a good relationship between VFA and CH 4 production for 156 temperate species, and a very strong relationship between VFA and total gas production. Collectively, these results suggest that among forages, stoichiometric relationships between VFA and CH 4 cannot be used, and that hydrogen produced by carbohydrate fermentation is not totally directed towards CH 4 production, at least in vitro.…”

Proceedings of the 10th International Symposium on the Nutrition of Herbivores

“…The consequent item included 64 antimethanogenic plants (Macheboeuf et al, 2014), of which 15 had strong effect (outliers of the methane=f (VFA) linear regression). The analysis for these plants generated from 29 to 161 peaks, with an average of 100.…”

“…The diets were prepared to be isotannic (20 g/kg of CT, except for the basal diet) and isoproteic (132 g/kg, adjusted with casein). The substrates were incubated in a batch system containing buffered rumen fluid from sheep at 39 °C (Macheboeuf et al, 2014). After 24 h of fermentation, the gas production and composition were recorded, and the fermentation end-product concentrations in the incubation medium and the in vitro DM disappearance (IVDMD) were determined.…”