Asparagopsis taxiformis and A. armata (Rhodophyta, Bonnemassoniaceae) two productive species of anti-methanogenic molecules for applications in cattle farms

Methane is a potent greenhouse gas (GHG) considered one of those responsible of global warming; for this reason, the world of research and industry is looking for a natural anti-methanogen agent. Those compounds are naturally present in macroalgae of the family Bonnemassoniaceae (Rhodophyta). Among them Asparagopsis species produce halo-organic compounds in specialized “gland cells”, as a natural defense against diseases and marine herbivory (Paul et al. 2006; Paul et al. 2011). The aim of present study was to test two red algae, Asparagopsis taxiformis and A. armata, collected from the Strait of Messina, Italy, as a source of anti-methanogenic compounds in cattle diet. DNA barcoded samples (BOLD #REAPP006-21, #REAPP004-21) were lyophilized and used at dietary inclusion levels (0, 2, and 4% as-fed basis) in an in vitro study to examine GHG production and volatile fatty acid (VFA) profiles. Asparagopsis taxiformis contained higher levels of bromoform, iodine and crude protein, than A. armata, which contained higher levels of acid and neutral detergent fibers. When lyophilized algae were supplemented in the diets total gas, butyrate and valerate production increased, while production CH4, acetate (A), propionate (P), A/P ratios and in vitro dry matter digestibility were reduced. Therefore, it may be possible to suppress methanogenesis both directly and indirectly by addition of Asparagopsis species which modified rumen fermentation profiles. To efficiently use seaweeds as feed ingredients with nutritional and environmental benefits, more research is required to determine the mechanisms underlying seaweed and dietary substrate interactions.