Exploration of Methane Mitigation Efficacy Using <i>Asparagopsis</i>-Derived Bioactives Stabilized in Edible Oil Compared to Freeze-Dried <i>Asparagopsis in Vitro</i>

Abstract

Asparagopsis oil products are of interest due to the stabilizing effects of the Asparagopsis-derived antimethanogenic bioactive compound bromoform (CHBr3). The objective of this in vitro series is to characterize antimethanogenic efficacy of freeze-dried Asparagopsis (FD-Asp) and Asparagopsis oil (Asp-Oil) and compare relative antimethanogenic response over time at multiple levels of CHBr3 delivery. Relative methane (CH4) emissions (mL/g) are based on in vitro apparent feed digested dry matter (IVDDM) after 24, 48, and 72 h of fermentation. CHBr3 contained in FD-Asp was included at 95, 191, and 286 mg/kg, and CHBr3 contained in Asp-Oil was included at 78, 117, and 175 mg/kg, to produce the Low, Mid, and High inclusions, respectively. Low FD-Asp had no significant impact on CH4 emissions, Mid FD-Asp demonstrated 91%, 44%, and 37% reductions, and the High FD-Asp demonstrated complete inhibition of CH4, after 24, 48, and 72 h of fermentation, respectively. Comparatively, Low Asp-Oil demonstrated a 46%, 28%, and 18% CH4 reduction, Mid Asp-Oil resulted in 99%, 92%, and 73% reductions, and the High Asp-Oil demonstrated complete inhibition of CH4 after 24, 48, and 72 h of fermentation, respectively. IVDDM and total volatile fatty acid (tVFA) production were not changed by the inclusion of FD-Asp and Asp-Oil. The results from this study show that Asparagopsis is not only a compelling CH4 mitigating feed supplement but is also able to be delivered in edible oil forms which will strengthen its applicability to on-farm use. This study is promising for the utility of Asp-Oil, and in vivo trials are essential to demonstrate the extent of efficacy of Asp-Oil in ruminant animals because FD-Asp has consistently demonstrated greater antimethanogenic efficacy in vivo compared to in vitro.