Although rumen modifiers are available now, a more realistic appraisal is that they hold promise for the future. To be fair, these products have been developed to increase productivity. The reduction of FCH4 has been an emergent 'value' that has suffered in the absence of an agreed price and obligation/market for CH4. A change from the current, unclear situation to international market agreement could generate clear, tangible co-benefits for the commercial manufacturers of such products.
Plant extracts such as allicin (for example garlic), bacteriocins and improved yeast products have reduced FCH4 by a range of mechanisms (McAllister and Newbold, 2008). Breeding for plant traits that have reduced
FCH4 has also been considered a medium-term possibility. One example has been the breeding of so-called 'high sugar' grasses (Abberton et al, 2008). On theoretical grounds, at least, ruminants fed by grazing 'high sugar' grass should require less feed to meet their ME requirement, so have reduced FCH4. A major challenge for animal scientists has been to clearly identify the specific plant chemical characteristics that reduced FCH4. This has not been a simple task. For forage-based diets, for example, proximate analysis has been unable to determine which diet components influence FCH4 (Hammond et al, 2009).
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