Effects of Nonesterified Fatty Acids From Different Plant-Derived Oils With Silica Gel Powder on In Vitro Gas Production and Ruminal Fermentation Characteristics.

Previous studies reported that nonesterified fatty acid in calcium salts has the possibility to mitigate methane emission when combined with silica powder. We investigated the effects of different lipase-treated oils, combined with silica powder as an oil adsorbent, on in vitro gas production and ruminal fermentation characteristics employing sheep ruminal fluid. In Experiment 1, treatments included five supplemental oils: palm kernel oil (PKO), palm oil (PO), sunflower oil (SFO), soybean oil (SBO), and linseed oil (LNO), supplemented levels at 2% and 4% of dry matter (DM) for each oil. Compared to the control (rolled barley substrate), supplementation with 4% DM of PKO, SBO, and LNO showed methane mitigation (p < 0.01). In Experiment 2, PKO, SBO, and LNO were further tested in either lipase-treated (NEFA) or untreated triglyceride (TG) to demonstrate effects of lipase treatment on fermentation characteristics. Although none of the TG differed in methane production, NEFA decreased methane production at 48 h, DM and crude protein (CP) disappearance (p < 0.05). Our findings suggest that lipase-treated PKO, SBO, and LNO supplementation, when combined with silica powder, can further suppress methane production; however, it also exerts negative impacts on DM and CP disappearances.