Methane emission by goats consuming diets with different levels of condensed tannins from lespedeza

Summary

This 21-day feeding trial on 24 yearling goats demonstrated that dietary inclusion of condensed tannin-rich Kobe lespedeza substantially reduced methane emissions compared to low-tannin sorghum-sudangrass forage, with methane output declining quadratically as lespedeza proportion increased from 0 to 100% (from 26.2 to 10.9 litres/day). The reduction appeared primarily attributable to condensed tannins rather than forage type per se, with in vitro rumen incubations and microbial enumeration suggesting direct inhibition of methanogenic bacterial activity. Ruminal protozoal populations increased linearly as tannin content declined, potentially contributing to the differential methane production observed.

Regional applicability

The study was conducted in the United States (likely by the University of New Mexico based on author affiliations) using tropical legume forages not widely grown in UK temperate systems. However, the mechanistic finding regarding condensed tannin inhibition of methanogenesis may inform UK research into methane mitigation through native temperate tannin-rich forages such as birdsfoot trefoil or sainfoin, which are candidates for pasture-based ruminant systems.

Key measures

Daily methane emission (litres/day, kJ/MJ gross energy, kJ/MJ digestible energy), gross energy digestibility, dry matter intake, in vitro ruminal methane production, total bacterial and protozoa counts in rumen fluid

Outcomes reported

The study measured methane (CH₄) emission from yearling goats consuming diets with varying levels of condensed tannin-containing Kobe lespedeza forage, and assessed ruminal microbial populations and in vitro methanogenesis in response to dietary treatments.

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