Determining the dose response for red seaweed to achieve methane mitigation in Merino sheep fed high-fibre diets

Abstract

<p>The macroalgae, <i>Asparagopsis spp.</i> naturally synthesizes and accumulates halogenated compounds such as bromoform, which has shown to be an effective enteric methane inhibitor. In sheep, a methane reduction of 80% was observed when <i>A. taxiformis</i> was included at 3% (OM basis) compared with the control (Li et al., 2018). Li et al. (2018) included the <i>Asparagopsis</i> in a modified total-mixed ration of a pelleted basal ration with additional crushed lupins as the carrier. Work in beef cattle (Kinley et al., 2020) reported high abatements (80% at 0.2% OM inclusion in comparison to the control) in a total-mixed ration. The effects of diet composition, namely increasing fibre content and influence on enteric methane abatement has also been reported (Roque et al., 2021), with lower abatement associated with higher dietary fibre. In Australia, most sheep are managed in extensive systems consisting of high-fibre forage diets and are unlikely to be offered a feed additive in a total mixed ration. At present, it is unknown what the recommended dietary inclusion level of <i>A. taxiformis</i> is for grazing systems, where animals are on a high-fibre diet. The aim of this study was to determine the dose-response of bromoform presented in a canola oil (SEAFEED™ SeaForest Pty Ltd) using a supplementary pellet as a carrier for sheep fed a high-fibre diet.</p>