Effects of marine and freshwater macroalgae on in vitro total gas and methane production.
This study aimed to evaluate the effects of twenty species of tropical macroalgae on in vitro fermentation parameters, total gas production (TGP) and methane (CH4) production when incubated in rumen fluid from cattle fed a low quality roughage diet. Primary biochemical parameters of macroalgae were characterized and included proximate, elemental, and fatty acid (FAME) analysis. Macroalgae and the control, decorticated cottonseed meal (DCS), were incubated in vitro for 72 h, where gas production was continuously monitored. Post-fermentation parameters, including CH4 production, pH, ammonia, apparent organic matter degradability (OMd), and volatile fatty acid (VFA) concentrations were measured. All species of macroalgae had lower TGP and CH4 production than DCS. Dictyota and Asparagopsis had the strongest effects, inhibiting TGP by 53.2% and 61.8%, and CH4 production by 92.2% and 98.9% after 72 h, respectively. Both species also resulted in the lowest total VFA concentration, and the highest molar concentration of propionate among all species analysed, indicating that anaerobic fermentation was affected. Overall, there were no strong relationships between TGP or CH4 production and the >70 biochemical parameters analysed. However, zinc concentrations >0.10 g x kg(-1) may potentially interact with other biochemical components to influence TGP and CH4 production. The lack of relationship between the primary biochemistry of species and gas parameters suggests that significant decreases in TGP and CH4 production are associated with secondary metabolites produced by effective macroalgae. The most effective species, Asparagopsis, offers the most promising alternative for mitigation of enteric CH4 emissions.
School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia ; Centre for Sustainable Tropical Fisheries and Aquaculture, James Cook University, Townsville, Queensland, Australia.
Lorenna
L
Machado
School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia ; Centre for Sustainable Tropical Fisheries and Aquaculture, James Cook University, Townsville, Queensland, Australia.
Marie
M
Magnusson
School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia ; Centre for Sustainable Tropical Fisheries and Aquaculture, James Cook University, Townsville, Queensland, Australia.
Nicholas A
NA
Paul
School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia ; Centre for Sustainable Tropical Fisheries and Aquaculture, James Cook University, Townsville, Queensland, Australia.
Rocky
R
de Nys
CSIRO Animal Food and Health Sciences, James Cook University, Townsville, Queensland, Australia.
Nigel
N
Tomkins
D000465:Algorithms; D000641:Ammonia / Q000378:metabolism; D000818:Animals; D001826:Body Fluids / Q000378:metabolism; D002417:Cattle; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005285:Fermentation; D005618:Fresh Water; D005740:Gases / Q000378:metabolism*; D005843:Geography; D006863:Hydrogen-Ion Concentration; D008697:Methane / Q000378:metabolism*; D008954:Models, Biological; D011793:Queensland; D012417:Rumen / Q000378:metabolism; D012623:Seawater; D012624:Seaweed / Q000145:classification / Q000378:metabolism*; D013997:Time Factors
D005232:Fatty Acids, Volatile; D005740:Gases; D000641:Ammonia; D008697:Methane