Probiotic Feed Additives Mitigate Odor Emission in Cattle Farms through Microbial Community Changes

Odor emissions from animal manure present a significant environmental challenge in livestock farming, impacting air quality and farm sustainability. Traditional methods, such as chemical additives and manure treatment, can be costly, labor-intensive, and less eco-friendly. Therefore, this study investigated the effectiveness of microbial feed additives in reducing these odors. Conducted over three months in 2022 on a Korean beef cattle farm with 20 cattle, the experiment involved feeding a mixture of four microbial strains—Bacillus subtilis KNU-11, Lactobacillus acidophilus KNU-02, Lactobacillus casei KNU-12, and Saccharomyces cerevisiae KNU-06. Manure samples were collected from an experimental group (n = 9) and a control group (n = 11), with microbial community changes assessed through 16S ribosomal RNA gene amplicon sequencing. The results demonstrated significant reductions in specific odorous compounds in the experimental group compared to the control group: ammonia decreased by 64.1%, dimethyl sulfide by 81.3%, butyric acid by 84.6%, and isovaleric acid by 49.8%. Additionally, there was a notable shift in the microbiome, with an increase in the relative abundance of Ruminococcaceae and Prevotellaceae microbes associated with fiver degradation and fermentation, while the control group had higher levels of Bacteroidota and Spirochaetota, which are linked to pathogenicity. This study demonstrates that probiotics effectively alter intestinal microbiota to enhance microorganisms associated with odor mitigation, offering a promising and more sustainable approach to reducing odor emissions in livestock farming.