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Objective Leader - Dr David Pacheco (AgResearch)
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Practical strategies to reduce agricultural greenhouse gas emissions are urgently sought, particularly for ruminant enteric methane, which forms 31% of New Zealand&#39;s total greenhouse gas inventory (Pinares-Patino <em>et al</em>, 2009).&nbsp; The most successful strategies will be those that lead to a profitable increase in animal productivity, as well as reducing net greenhouse gas emissions, not just those of enteric methane alone.
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Dietary fat supplements, especially those containing unsaturated fatty acids, can reduce enteric methane emissions, but oil production for animal feed is usually associated with increased net greenhouse gas emissions (Beauchemin <em>et al</em>, 2008, 2009; Grainger <em>et al</em>, 2010).&nbsp; Eicosahexanoic acid (EPA or C20:5) and Docosahexanoic acid (DHA or C22:6) are the major bioactive unsaturated fatty acids found in fish oil and marine algae (Givens <em>et al</em>, 2000).&nbsp; <em>In-vitro</em> studies suggest that EPA and DHA may reduce methane emissions by up to 80% (Fievez <em>et al</em>, 2003) and marine algae by greater than 92% (Bozic <em>et al</em>, 2009).&nbsp; 
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A commercial DHA microalgae supplement has been shown to reduce dry matter intake and increase milk yield of dairy cows (Boeckaert <em>et al</em>, 2008).&nbsp; Seaweeds and algae are more digestible than many terrestrial plants, due to less cellulose and more starch.&nbsp; However, <em>in-vivo</em> trials feeding algae or algae products where methane emissions have been measured have not yet appeared in the peer-reviewed literature, although it is understood these are underway in Australia (Chris Grainger, pers comm., Tony Parker, pers comm.).
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Microalgae offer a means of supplementing animals with a source of unsaturated fatty acids with believed potent methane mitigation potential that will reduce net greenhouse gas emissions.&nbsp; Microalgae of freshwater and marine origin can be cultivated to treat wastewaters of human, agricultural and industrial origin e.g. from sewage and effluents from dairy farms, piggeries, aquaculture facilities and fossil fuel fired power stations.&nbsp; 
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New Zealand research by NIWA has developed wastewater treatment high rate algal ponds and there are several demonstration facilities that could provide sufficient biomass for harvest and potential use as a methane-mitigating animal feed supplement.&nbsp; Meanwhile, in Australia, researchers at James Cook University (T. Parker and R. de Nys) have been attempting to feed marine macroalgae cultivated in the University algal farm to cattle to reduce methane emissions.&nbsp; However, they have recently moved to producing freshwater microalgae to avoid suspected iodine toxicity in cattle initially fed algae of marine origin.&nbsp; These researchers are also to test a microalgal meal, a bi-product from microalgal oil production from a bio-sequestration &lsquo;algal synthesiser&#39; farm associated with a coal-fired power station, for methane mitigation potential in cattle (T. St Clair and T. Parker, pers comm.).
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This project capitalises on these very recent developments to keep New Zealand at the forefront of enteric methane mitigation research.&nbsp; Microalgal supplements of NZ and Australian origin will be evaluated for methane mitigation potential in sheep using the &lsquo;gold-standard&#39; calorimetry facility at AgResearch.&nbsp; If successful, we may have a nutrition supplement capable of both reducing methane emissions and enhancing animal production, at a reduction in net greenhouse gas emissions.
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