Effects of Gelidium sp. Extract Supplementation on Rumen Fermentation, Methane Emission, and Fatty Acid Profile In Vitro

This study evaluated the effects of Gelidium sp.extract (GE) supplementation as a natural phenolic source on in vitro ruminal fermentation, nutrient digestibility, gas production, and fatty acid profile in a high-unsaturated fatty acid diet.The basal diet consisted of elephant grass (60%) and concentrate (40%) composed of wheat pollard, soybean meal, and sunflower oil.Treatments included four levels of Gelidium sp.extract (0, 1, 2, and 3% of diet DM; GE0-GE3).In vitro incubations were conducted using the gas production technique and the two-stage digestibility method.Supplementation with GE decreased ruminal crude protein digestibility (IVCPD), protease activity, protozoa population, and methane production (P < 0.05), while total IVCPD increased at GE3.No effects were observed on in vitro dry matter, organic matter, or crude fiber digestibility, gas production kinetics, or CMCase activity.Supplementation at ≥2% reduced saturated fatty acids, particularly stearic acid, while increasing oleic, linoleic, and total unsaturated fatty acids in the rumen.In conclusion, Gelidium sp.extract supplementation modulated ruminal protein metabolism, methane emissions, and lipid biohydrogenation, thereby enhancing the preservation of unsaturated fatty acids without impairing overall fermentation or digestibility.