Ruminal fermentation and enteric methane production of legumes containing condensed tannins fed in continuous culture

Authors: ROCA-FERNANDEZ, ANA - Universidad De Chile; DILLARD, LEANNE - University Of Auburn; Soder, Kathy

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2020
Publication Date: 5/28/2020
Citation: Roca-Fernandez, A., Dillard, L.L., Soder, K.J. 2020. Ruminal fermentation and enteric methane production of legumes containing condensed tannins fed in continuous culture. Journal of Animal Science. 103(8):7028-7038. https://doi.org/10.3168/jds.2019-17627.
DOI: https://doi.org/10.3168/jds.2019-17627

Interpretive Summary: Compounds in plants, such as condensed tannins, may reduce methane production in cattle. However, tannins may also have negative impacts on ruminal fermentation. We evaluated four legumes (alfalfa, birdsfoot trefoil, crown vetch, and sericea lespedeza), with varying concentrations of tannins, to evaluate effects on ruminal fermentation and methane production in a continuous culture fermentor system. The forage with the greatest tannin concentration (sericea lespedeza) had the lowest methane production, but also had decreased ruminal fermentation, which may result in reduced animal productivity (e.g., meat or milk production). Further work should be conducted to find optimal diets to reduce methane production without negatively affecting nutrient digestibility to maintain or improve animal productivity while reducing negative environmental impacts.

Technical Abstract: A continuous culture fermentor study was conducted to assess nutrient digestibility, VFA concentrations, microbial protein synthesis, bacterial N efficiency and enteric methane (CH4) production of 4, 50:50 grass-legume diets, randomly assigned in a 4 × 4 Latin square design. Four legumes, containing increasing condensed tannin (CT) concentrations, were tested: alfalfa [ALF; Medicago sativa L., non-CT legume]; birdsfoot trefoil [BFT; Lotus corniculatus L., low CT legume]; crown vetch [CV; Securigera varia L., moderate CT legume]; and sericea lespedeza [SL; Lespedeza cuneata (Dum. Cours.) G. Don, high CT legume]. Orchardgrass (Dactylis glomerata L.) was the grass used in all diets. Four fermentors were evaluated over 4 periods, with 7 d for adaptation and 3 d for sample collection. Each fermentor was fed 82 g DM/d in equal portions 4 times daily at 0730, 1030, 1400 and 1900 h. Temperature and pH were recorded every 2 min. The CH4 output was recorded every 10 min. Effluent samples were collected during the last 3 d of the experiment, composited by fermentor and period, and analyzed for pH and VFA as well as DM, OM, CP, NDF and ADF for determination of apparent (DM, OM, NDF and ADF) and true (DM and OM) nutrient digestibilities. Microbial protein synthesis and bacterial efficiency were estimated by analysis of N flows and purines. Grass and legumes were evaluated for DM, OM, CP, NDF, ADF, minerals and CT concentrations. Data were statistically analyzed by the GLIMMIX procedure of SAS. The CT concentrations were 3, 21, 38 and 76 g/kg DM for ALF, BFT, CV and SL, respectively. The SL had decreased (P < 0.001) NDF and ADF digestibilities, total VFA concentration and N intake compared to all other treatments. This resulted in total CH4 production (P < 0.001) in the SL diet being the least of all treatments. Bacterial N efficiency per kg of truly digested DM and OM were lower (P = 0.05) in SL than in BFT and CV. The lowest (P < 0.001) CH4 production per unit of digestible nutrients was found in SL. There was a negative correlation (P < 0.001) between CT concentration and CH4 production. Tradeoffs in ruminal fermentation (reduced nutrient digestibility, VFA concentration and bacterial N efficiency) were found in SL. Future work is needed to find optimal diets for reducing CH4 emissions without negatively affecting ruminal digestion and to evaluate the effect of CT legumes on biohydrogenation process, microbial populations, voluntary intake and animal productivity.