In vitro ruminal fermentation of fenugreek (Trigonella foenum-graecum L.) produced less methane than that of alfalfa (Medicago sativa)

Abstract

Objective: The objective of this study was to compare fenugreek (FG) with alfalfa (Alf) in ruminal fermentation and methane (CH₄) production <i>in vitro</i>.Methods: Whole-plant FG harvested at 11- and 15-wk and Alf harvested at early and mid-bloom maturities, alone or as 50:50 mixture of FG and Alf at the respective maturity, were assessed in a series of 48-h <i>in vitro</i> batch culture incubations. Total fermentation gas and methane gas production, dry matter (DM) disappearance, volatile fatty acids, microbial protein and 16S RNA gene copy numbers of total bacteria and methanogens were determined.Results: Compared to early bloom Alf, FG harvested at 11-wk exhibited higher (p<0.05) <i>in vitro</i> DM and neutral detergent fibre disappearance, but this difference was not observed between the mid-bloom Alf and 15-wk FG. Regardless plant maturity, <i>in vitro</i> ruminal fermentation of FG produced less (p<0.001) CH₄ either on DM incubated or on DM disappeared basis than that of Alf during 48-h incubation. <i>In vitro</i> ruminal fermentation of FG yielded similar amount of total volatile fatty acids with higher (p<0.05) propionate percentage as compared to fermentation of Alf irrespective of plant maturity. Microbial protein synthesis was greater (p<0.001) with 11-wk FG than early bloom Alf as substrate and 16S RNA gene copies of total bacteria was higher (p<0.01) with 15-wk FG than mid-bloom Alf as substrate. Compared to mid-bloom Alf, 15-wk FG had lower (p<0.05 to 0.001) amount of 16S RNA methanogen gene copies in the whole culture during 48-h incubation.Conclusion: In comparison to Alf, FG emerges as a high quality forage that can not only improve rumen fermentation <i>in vitro</i>, but can also remarkably mitigate CH₄ emissions likely due to being rich in saponins.