Tannin-mediated improvement of Moringa oleifera silage: nutritional quality, aerobic stability, and methane mitigation

Methane emissions during livestock production have become an important source of greenhouse gases. Silage feed, as the main feed source for ruminants, plays a significant role in the livestock industry. In this experiment, three different tannin-related compounds (tannic acid, gallic acid and polyethylene glycol) were added as silage additives to Moringa oleifera leaf silage. Their effects on the nutritional quality, fermentation quality, aerobic stability and microbial community of Moringa oleifera leaf silage were determined, and in vitro experiments were conducted to determine their influence on rumen methane emissions. Showed that TA and GA increased dry matter and true protein content while reducing neutral detergent fiber, the ratio of non-protein nitrogen to total nitrogen, and ammonia nitrogen levels (P < 0.05). TA enhanced aerobic stability for the first three days of aerobic exposure, whereas the 1% GA treatment maintained a stable pH value throughout the aerobic exposure period (4.19–4.27). Both TA and GA significantly reduced in vitro methane emissions without compromising dry matter digestibility (P < 0.05), among them, the 1% GA group reduced methane emissions by 21.3% compared to the CK (32.67 ml vs 41.52 ml). In contrast, PEG promoted lactic acid bacteria growth and lactic acid accumulation while inhibiting undesirable microorganisms such as Enterobacter; however, its overall impact on silage preservation was limited. These findings suggest that 1% GA could serve as a sustainable silage additive, effectively improving silage quality and aerobic stability while reducing greenhouse gas emissions. This experiment indicates that tannin compounds, especially gallic acid, can be chosen as an additive for Moringa oleifera leaf silage, which is conducive to the sustainable development of the livestock industry.