The sustainable mitigation of ruminal methane and carbon dioxide emissions by co-ensiling corn stalk with Neolamarckia cadamba leaves for cleaner livestock production

Greenhouse gas emissions from ruminants, including methane (CH₄) and carbon dioxide (CO₂), make a significant contribution to global warming. Exploring novel and effective approaches for reducing ruminant greenhouse gas emissions is essential for cleaner livestock production and alleviating global warming. To investigate the effectiveness of a new feed source, Neolamarckia cadamba leaves (NCL), in reducing greenhouse gas emissions from ruminants as well as the underlying mechanism, 0%, 10%, 30%, and 50% NCL were ensiled with corn stalk in two trials. The results indicated that NCL inclusion increased the crude protein content (P < 0.01) and lowered the ammonia-N and fiber contents of the silage (P < 0.01 for both). The silage samples were fermented anaerobically in vitro in buffered rumen fluids at 39 °C. NCL did not affect ruminal fermentation characteristics; however, dry matter degradability was increased (P < 0.05), whereas CH₄ (32.7 vs 27.8 mL/g digestible dry matter [DM]) and CO₂ (132 vs 114 mL/g digestible DM) production were decreased. The microbial composition of the fermentation fluid was analyzed by qPCR and next-generation sequencing. The results showed that NCL inclusion reduced the bacterial and archaeal count (P < 0.05) in the ruminal fluid, increased the relative abundance of Prevotella and Succiniclasticum (P < 0.05), and decreased that of Ruminococcaceae_NK4A214, Ruminococcaceae_UCG-010 and Christensenellaceae_R-7 (P < 0.05). Our results indicated that NCL inclusion can be used to restrict proteolysis and increase the nutritive value and digestibility of corn stalk silage. Furthermore, mixing NCL in the feed may represent a dietary manipulation strategy to reduce CH₄ and CO₂ production by ruminants without adversely affecting ruminal fermentation. Consequently, NCL can be recommended for widespread use to achieve a sustainable and cleaner animal production, and for the mitigation of global warming.