Mannan oligosaccharides reduce the carbon footprint by decreasing methane emission and nitrogen excretion in Xiangdong black goats

Methane emission represents both an environmental concern and a loss of feed energy for ruminants. This study investigated the effects of supplementing 2.0 % mannan oligosaccharides (MOS) on energy utilization, nitrogen excretion, and methane emissions in twelve Xiangdong black goats. Compared to the control group, MOS supplementation significantly reduced CH₄ and CO₂ emissions, lowered fecal, urinary, and methane energy losses, and increased the energy retention rate of goats (P < 0.05). Numerically, MOS improved the apparent digestibility of DM, CP, NDF, ADF and net protein utilization while decreasing fecal nitrogen and urinary nitrogen excretion, although these effects were not statistically significant (P > 0.05). In addition, feeding MOS also reduced the activity of methyl-CoM, methyl-CoM reductase, electron branching enzyme and the abundance of Methanobrevibacter in the rumen of goats, though these effects were not statistically significant (P > 0.05). Most importantly, MOS enhanced the activity of the acetogenic bacteria Acetitomaculum and Prevotella, which enhanced their ability to compete with methanogens for H₂ and reduced CH₄ emissions. It can be concluded that MOS can improve the rumen micro-ecological environment, improve the utilization efficiency of nutrients and reduce the carbon footprint of Xiangdong black goats.