Micro- and Macro-Algae Combination as a Novel Alternative Ruminant Feed with Methane-Mitigation Potential

SIMPLE SUMMARY: Considering the current challenges facing the modern livestock industry and the food insecurity situation, there is an urgent need to find alternative, sustainable, climate-friendly, and safe feed ingredients. This study provides a novel solution with the mixture of Euglena gracilis and Asparagopsis taxiformis as a feed for ruminants. Euglena gracilis is a highly nutritive material that can be used to partially replace the expensive, high-quality ingredients in the diet. Due to its bromoform content, Asparagopsis taxiformis is efficacious in reducing methane emissions. However, there are some health concerns for animals and humans with regard to its usage, as well as some doubts about the mass production that is required to achieve effective methane reduction. Therefore, the current study evaluated a new formulation composed of the minimum effective levels of Euglena and Asparagopsis to partially replace the concentrate mixture in the ruminant diet and reduce methane emissions. This combination had a synergistic effect in reducing methane production that was better than supplementing these algae individually and had no adverse impacts on animal productivity indices. Therefore, this intervention has double-sided benefits, providing high-quality alternative feed and reducing methane emissions with lower amounts of Asparagopsis. ABSTRACT: This study was conducted to provide alternative high-quality feed and to reduce methane production using a mixture of the minimum effective levels of Euglena gracilis, EG, and Asparagopsis taxiformis, AT. This study was performed as a 24 h in vitro batch culture. Chemical analysis demonstrated that EG is a highly nutritive material with 26.1% protein and 17.7% fat. The results showed that the supplementation of AT as a feed additive at 1 and 2.5% of the diet reduced methane production by 21 and 80%, respectively, while the inclusion of EG in the diet at 10 and 25% through partially replacing the concentrate mixture reduced methane production by 4 and 11%, respectively, with no adverse effects on fermentation parameters. The mixtures of AT 1% with both EG 10% and EG 25% had a greater reductive potential than the individual supplementation of these algae in decreasing methane yield by 29.9% and 40.0%, respectively, without adverse impacts on ruminal fermentation characteristics. These results revealed that the new feed formulation had a synergistic effect in reducing methane emissions. Thus, this approach could provide a new strategy for a sustainable animal production industry.