In vitro screening of anti-methanogenic additives for use in Australian grazing systems

Abstract

Despite considerable effort to develop and optimise additives to reduce methane emissions from cattle, little information on additive effectiveness exists for cattle under grazing scenarios. As the majority of Australian cattle production occurs on grazing land it is pertinent to report on the use of additives under simulated conditions. The current study evaluated the addition of nine additives to Rhodes grass hay under in vitro conditions, to estimate their impact on methane (CH4), gas production, and rumen fermentation parameters (volatile fatty acids, rumen pH and in vitro dry matter digestibility [IVDMD]). Citral extract at 0.1% of rumen media decreased all CH4 production parameters, but reduced gas production and digestibility, compared to a 100% hay control. Similarly, Sandalwood essential oil decreased CH4 production at 48 h, IVDMD and gas production, compared to the control. Biochar + nitrates at 5 and 8% DM, and Biochar + Asparagopsis at 5% DM decreased cumulative CH4 production (15.6%, 25.9%, 23.8%, respectively; P < 0.01), compared to the control. No changes in IVDMD and gas production were observed. As such, the biochar additives were considered the most promising additives from those evaluated with a substrate designed to replicate Australian grazing systems.

Synergistic Effects of Essential Oil Blends and Fumaric Acid on Ruminal Fermentation, Volatile Fatty Acid Production and Greenhouse Gas Emissions Using the Rumen Simulation Technique (RUSITEC)

“…In support, a meta-analysis showed that supplementation of Agolin ® Ruminants (coriander seed oil, eugenol, geranyl acetate, geraniol, and fumaric acid) produced no significant variation in the rumen pH of Holstein dairy cows [32]. On the contrary, several in vitro batch culture studies on individual or blends of essential oils, with or without fumaric acid, reported significant differences in ruminal pH [5,27,31,33]. Essential oils (EOs) have been reported to elevate rumen pH, either numerically [9,23] or significantly [15] when compared to control diets [31].…”

Meta-Analysis and Ranking of the Most Effective Methane Reduction Strategies for Australia’s Beef and Dairy Sector

“…Badgery et al [16] found that Biserrula pelecinus has great potential to reduce enteric CH 4 emissions, similarly to clover Trifolium subterraneum. Stifkens et al [51] found that increasing the proportion of legumes such as Leucaena leucocephala in feed reduces CH 4 due to condensed tannins acting as a bioactive compound that reduce methanogenesis. A 36% inclusion of Leucaena leucocephala in the diet of cattle reduced CH 4 by 25.09% per kilogram of boneless trimmed beef.…”

“…Ridoutt et al [43] explored the supplement of Asparagopsis taxiformis, a red seaweed, on feedlot cattle's CH 4 production and calculated a 1-4% reduction in Australia's cattle sector. Parra et al [51] assessed a range of additives to reduce CH 4 in grazing cattle and found the addition of biochar and nitrate, biochar and Asparagopsis, and citral extract to significantly reduce CH 4 emissions by 22.83%, 19.82%, and 41%, respectively. Lean and Moate [20] reviewed CH 4 reduction strategies in Australia and found that nitrate supplementation reduced emissions by 10% and feed supplemented with 3-nitro-oxypropanol (3-NOP) reduced CH 4 by 22% in beef cattle and 39% in dairy cattle.…”

“…Improve Parra et al 2023 [51] In vitro screening of anti-methanogenic additives for use in Australian grazing systems Study of methane reduction over 48 h of incubating rumen fluid in vitro testing with garlic powder, biochar and nitrates, biochar and Asparagopis Taxiformis, essential oil blend, citral extract, sandalwood essential oil, Bacillus probiotic additive, and sugar cane extract.…”

“…Inclusion of Asparagopis was the highest cost due to requirement for establishing new industry [84]. Supplementation with Asparagopis and with citral were considered to be not technologically ready due to requirements for Asparagopis commercialisation [78], and further research for citral at higher-than-recommended doses due to digestion effects is needed [51].…”