Sustainable beef production: Utilizing tea by-products for methane mitigation and productivity enhancement

Globally abundant tea by-products (TBP) are an underexploited reservoir of natural flavonoids with methane (CH 4 ) mitigation potential. This study innovatively developed a closed-loop framework integrating chemical characterization, in vitro screening, in vivo validation, and mechanistic elucidation. Systematic chemical profiling of 30 TBP identified distinct proximate and flavonoid compositions, revealing that green TBP are rich in catechins, whereas black TBP are dominated by theaflavins. In vitro screening determined 2% DM as the optimal dose (CH 4 reduction up to 22.29%), and this effect was significantly correlated with tea polyphenol content. 16 S r RNA analysis showed TBP supplementation increased Succinivibrionaceae_UCG-002 and decreased Methanobrevibacter relative abundance. Subsequently, a 150-day feeding trial was conducted with finishing Angus steers supplemented with Anshun green tea residue (ASGT, selected for in vitro efficacy and palatability). Forty-five individually housed Angus steers were randomized into three groups (0, 75, and 150 g/d ASGT). The 75 g/d supplementation enhanced average daily gain and improved feed efficiency, while the 150 g/d dose achieved greater CH 4 reduction (14.41 kg CH 4 /steer/year, 10.1% lower than control). Metagenomic analysis elucidated the microbial mechanism: ASGT enriched propionate-producing bacteria (e.g., Prevotella ), suppressed hydrogenotrophic methanogens (e.g., Methanobrevibacter ), altered carbohydrate-active enzyme profiles and hydrogenase group composition, and functionally downregulated key methanogenic enzymes (e.g., methyl-coenzyme M reductase) while upregulating pathways for the TCA cycle and propionate metabolism . This study provides the first complete evidence chain supporting TBP as a natural dual-purpose additive that reduce beef cattle carbon footprint and improve productivity, addressing agricultural waste valorization and climate-smart livestock production for sustainable beef industry intensification.