Network analysis and functional estimation of the microbiome reveal the effects of cashew nut shell liquid feeding on methanogen behaviour in the rumen

Koki Maeda¹, Van Thu Nguyen², Tomoyuki Suzuki^1,3, Keita Yamada⁴, Kushi Kudo^4,5, Chie Hikita⁶, Thanh Phong Le², Minh Chon Nguyen², and Naohiro Yoshida^4,7

¹ Crop, Livestock & Environment Division, Japan International Research Center for Agricultural Sciences (JIRCAS), 1-1 Ohwashi, Tsukuba, Ibaraki 305-8686, Japan.

² Faculty of Agriculture, Can Tho University, Campus II, 3/2 St, Ninh Kieu, Can Tho, Vietnam.

³ Central Region Agricultural Research Center, National Agriculture and Food Research Organization (NARO), 768 Senbonmatsu, Nasu-shiobara, Tochigi 329-2793, Japan.

⁴ Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502, Japan.

⁵ Faculty of Human Development and Environment, Kobe University, 3-11 Tsurukabuto, Nada-ku, Kobe 657-8501, Japan.

⁶ Idemitsu Kosan, Co. Ltd., 2-1 Midorigahara, Tsukuba, Ibaraki 300-2646, Japan.

⁷ Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152- 8550, Japan.

Summary

The effects of cashew nut shell liquid (CNSL) feeding on the methane (CH₄) emission and the ruminal microbiome of Lai Sind beef cattle were investigated. Changes in the methane production and rumen microbiome by CNSL feeding were monitored by a respiration chamber and 16S rRNA gene amplicon sequencing respectively. The results demonstrated that CNSL feeding mitigated 20.2%–23.4% of the CH₄ emission in vivo without apparent adverse effects on feed intake and feed digestibility. The rumen fluid analysis revealed a significant increase in the proportion of propionate in the total short-chain fatty acids. The relative abundance of methanogen (order Methanobacteriales) decreased significantly, indicating the direct inhibitory effect of CNSL on methanogens. The predicted function of the rumen microbiome indicated that carbohydrate and lipid metabolisms including propionate production were upregulated by CNSL feeding, whereas CH₄ metabolism was downregulated. A network analysis revealed that methanogen changed its partner bacteria after CNSL feeding. The δ¹³C of CH₄ ranged from −74.2‰ to −66.6‰ with significant fluctuation by CNSL feeding, in agreement with the shift of the rumen microbiome. Our findings demonstrate that CNSL feeding can mitigate the CH₄ emission from local cattle production systems in South-East Asia by modifying the rumen microbiome and its function.