Evaluation of Two Species of Macroalgae from Azores Sea as Potential Reducers of Ruminal Methane Production: In Vitro Ruminal Assay.

Simple Summary: This research evaluates the nutritional value and mineral content of two red algae species from the Azorean Sea, Asparagopsis taxiformis (native) and Asparagopsis armata (invasive). The aim is to assess their impact on in vitro rumen fermentation characteristics, including total gas and methane production, when added to a substrate of grass. The study finds that both algae species exhibit high protein levels (≈23.5% DM) and significant amounts of magnesium (1.15% DM) sodium (8.6% DM) and iron (2851 ppm). Furthermore, it was demonstrated that the addition of A. taxiformis at a concentration of 5% resulted in an 84% reduction in enteric methane production within the first 24 h, whereas A. armata, at the same concentration, reduced methane production by 34%. These in vitro findings suggest that Asparagopsis species from the Azorean Sea have potential as effective protein and mineral supplements, offering the additional benefit of reducing methane emissions from rumen fermentation. The utilisation of seaweeds as feed supplements has been investigated for their potential to mitigate enteric methane emissions from ruminants. Enteric methane emissions are the primary source of direct greenhouse gas emissions in livestock and significantly contribute to anthropogenic methane emissions worldwide. The aim of the present study is to evaluate the nutritional role and the in vitro effect on cumulative gas and methane production of Asparagopsis taxiformis (native species) and Asparagopsis armata (invasive species), two species of red algae from the Azorean Sea, as well as the ability to reduce biogas production when incubated with single pasture (Lolium perenne and Trifollium repens) as substrate. Four levels of concentrations marine algae were used (1.25%, 2.25%, 5%, and 10% DM) and added to the substrate to evaluate ruminal fermentation using the in vitro gas production technique. The total amount of gas and methane produced by the treatment incubation was recorded during 72 h of incubation. The results indicate that both algae species under investigation contain relatively high levels of protein (22.69% and 24.23%, respectively, for Asparagopsis taxiformis and Asparagopsis armata) and significant amounts of minerals, namely magnesium (1.15% DM), sodium (8.6% DM), and iron (2851 ppm). Concerning in vitro ruminal fermentation, it was observed that A. taxiformis can reduce enteric methane production by approximately 86%, during the first 24 h when 5% is added. In the same period and at the same concentration, A. armata reduced methane production by 34%. Thus, it can be concluded that Asparagopsis species from the Azorean Sea have high potential as a protein and mineral supplement, in addition to enabling a reduction in methane production from rumen fermentation. [ABSTRACT FROM AUTHOR]