AUTHOR=Malik Pradeep Kumar , Trivedi Shraddha , Kolte Atul Purushottam , Mohapatra Archit , Bhatta Raghavendra , Rahman Habibar 

TITLE=Effect of an anti-methanogenic supplement on enteric methane emission, fermentation, and whole rumen metagenome in sheep

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.1048288

DOI=10.3389/fmicb.2022.1048288

ISSN=1664-302X

ABSTRACT=<p>A study was conducted to investigate the impact of an anti-methanogenic product supplementation on enteric methane emissions, whole rumen metagenome and ruminal fermentation in sheep. Twelve adult male sheep were randomly divided into two groups of six animals each. Animals were fed <italic>ad libitum</italic> on a total mixed ration either without (CON) or with an anti-methanogenic supplement (Harit Dhara-HD). The anti-methanogenic supplement contained 22.1% tannic acid in a 3: 1 ratio of condensed and hydrolysable tannins. The supplementation of product revealed a significant reduction in daily enteric methane emission (21.9 vs. 17.2 g/d) and methane yield (23.2 vs. 18.2) without affecting the nutrient intake and digestibility. However, the propionate concentration in the HD treatment group was significantly higher than in the CON group. On the contrary, the ammonia nitrogen concentration was lower. The anti-methanogenic supplement significantly decreased the ruminal protozoa in the HD treatment group. Whole rumen metagenome analysis revealed that the core bacterial (<italic>Bacteroidetes</italic> and <italic>Firmicutes</italic>) and archaeal communities (<italic>Methanobrevibacter</italic> and <italic>Methanosarcina</italic>) were comparable between the CON and HD treatment groups. However, the supplementation of anti-methanogenic product led to a considerable reduction in the abundance of <italic>Proteobacteria</italic>, whereas the abundance of <italic>Lentisphaerae</italic> was greater. The supplementation significantly decreased the abundance of <italic>Methanocaldococcus</italic>, <italic>Methanococcoides</italic>, <italic>Methanocella</italic>, and <italic>Methanoregula</italic> methanogens. A total of 36 KO related to methanogenesis were identified in this study. The activities of formate dehydrogenase (EC 1.8.98.6) and tetrahydromethanopterin S-methyltransferase (EC 2.1.1.86) were significantly lowered by the anti-methanogenic product supplementation in sheep. In conclusion, the anti-methanogenic supplement has the potential to decrease enteric methane emission (~22%) at the recommended level (5% of DM) of supplementation. The contribution of minor methanogens vulnerable to supplementation to rumen methanogenesis is not known; hence, the culturing of these archaea should be taken on priority for determining the impact on overall rumen methanogenesis.</p>