Cashew nut shell liquid (CNSL) is an effective rumen modulator that reduces methane emissions and shifts fermentation patterns without adverse effects on animal performance, found a meta-analysis performed by Slamet Widodo, a Doctoral Degree Student in Natural Resources and Environmental Management Science at Indonesia’s IPB University, together with his team.
This parallel meta-analysis was conducted using data from 11 in vitro and 16 in vivo studies. Using the meta and metafor packages in R software, the weighted mean difference (WMD) was estimated under a random-effects model to assess the effects of CNSL on enteric methane emissions, rumen fermentation characteristics, and production performance.
Supplementation with CNSL demonstrated a significant mitigation potential in the in vitro systems, with a 51.91% reduction in methane production (p < 0.04) and a 19.03% increase in propionate concentration (p < 0.001).
This mechanistic potential was validated in vivo, where CNSL significantly shifted fermentation stoichiometry (+22.15% propionate; −6.30% acetate) and reduced methane yield (g/kg dry matter intake) by 20.14% (p = 0.006).
Supplementation with CNSL reduced emissions across both systems without compromising in vitro dry matter digestibility (p = 0.69) or in vivo dry matter intake (p = 0.51) and milk yield (p = 0.55).
Subgroup analysis revealed that efficacy was species-dependent, with swamp buffalo and beef cattle exhibiting stronger propionate responses than dairy cattle.