Advancing methane mitigation in ruminants through feed additive combinations: efficacy, interactions, and implementation challenges

Feed additives have emerged as promising strategies to lower enteric methane (CH₄) emissions, with some achieving reductions of up to 30%. However, their widespread adoption is limited by inconsistent effects on productivity, regulatory barriers, and economic constraints. Combining feed additives with complementary modes of action might enhance mitigation outcomes, yet results vary depending on diet, adaptation period, additive interaction, and microbial dynamics in the rumen. This review synthesizes current knowledge on the efficacy, interaction effects, and implementation potential of feed additive combinations. It also examines economic incentives, such as carbon credit schemes, and recent policy developments that could accelerate adoption. While in vitro studies often show promising results, validation of combinations of feed additives in large-scale production systems is lacking. The complexity of hydrogen metabolism and microbial adaptation underscores the need for more integrated research efforts. Optimizing additive combinations that not only reduce CH₄ but also support animal productivity is essential for developing sustainable, climate-smart livestock systems.