Evaluation of a Colombian oregano oil (Lippia origanoides Kunth) and a novel yeast product from Pichia guilliermondii, alone or in combination, on rumen fermentation, methanogenesis and microbiome in the Rumen Simulation Technique

In this study, Lippia origanoides Kunth, native of the Patía region in Southwest Colombia, and Pichia guilliermondii LV196, an inactivated yeast from the germplasm bank of Agrosavia (Colombian Agricultural Research Corporation), alone or combined, were tested for their long-term effect on rumen fermentation and methanogenesis whilst also characterising their effect on bacterial and methanogen communities. When added to a rumen simulating fermentor (RUSITEC), Lippia origanoides Kunth at 132 microliters/d had a detrimental effect on rumen fermentation which was accompanied by a reduction in the relative abundance of protozoa and fungi and a profound impact on the bacterial and archaeal communities. Pichia guilliermondii LV196 at 0.5 g/L, however, had no effect on fermentation parameters or nutrient utilization, and neither changes in microbial abundances or in the structure of bacterial and archaeal communities were observed. Further studies with lower doses of the essential oil and higher doses of the yeast product are needed to explore the potential of these feed additives, either alone or combined, to enhance productivity whereas reducing methane emissions.