Effectiveness of Tannin-Rich Plants for Mitigating Enteric Methane Emissions in African Ruminant Systems: Evidence from South Africa—A Systematic Review

Enteric methane (CH4) emissions from ruminants are a significant contributor to agricultural greenhouse gas emissions and represent an increasing concern in African livestock systems. This systematic review evaluates the effectiveness of tannin-rich plants as a dietary strategy for mitigating enteric CH4 emissions in African ruminant production systems. The review followed PRISMA guidelines and included peer-reviewed original studies published between 2015 and 2025 that investigated tannin-rich plant interventions in cattle, sheep, or goats within African production systems. Eligible studies comprised both in vivo feeding trials and in vitro rumen fermentation experiments. Studies were included if they reported enteric CH4 or greenhouse gas-related outcomes, while reviews, modeling studies, non-ruminant studies, and studies without CH4-related outcomes were excluded. A total of eight eligible studies were identified, all conducted in South Africa despite the Africa-wide scope of the review. Overall, tannin-rich plant interventions showed potential to reduce CH4 emissions, although the magnitude and consistency of responses varied depending on tannin type, source, inclusion level, form of administration, and dietary context. Purified and encapsulated tannin extracts generally produced more consistent CH4 reductions than crude or whole-plant sources. Responses also differed between controlled total mixed ration systems and forage-based feeding systems. However, the small number of studies and their strong geographic concentration limit broader generalization across the continent. In conclusion, tannin-rich plants show promise as a natural CH4 mitigation strategy in ruminants, but more regionally distributed and methodologically robust studies are needed across Africa to strengthen the evidence base.