eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2017-03-25 14 1 145 152 10.13005/bbra/2429 22445 article Hamed Amini Pour 1 Abbas-Ali Naserian 2 Ali-Reza Vakili 2 Abdol-Mansour Tahmasbi 2 Ph.D Student of Ruminant Nutrition, Ferdowsi University of Mashhad International Campus, Mashhad, Iran. Department of Animal Sciences, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran. The subject of this research was to evaluate the effect of adding different levels (0, 2ml) essential oils of thyme (Thymus) and Menthapiperita (Carvacrol) on alfalfa silagedegradability byin vitro gas production and in vitro gas production kinetics. In vitro gas production values were determined by using rumen liquor from three lactation Holstein cows in times of 2, 4, 6, 8, 12, 16, 24, 48, 72 and 96 hours. The results of this paperreport that, the effects of essential oils of thyme (Thymus) and Menthapiperita (Carvacrol) were significant. In vitro gas production was decreased by essential oils of thyme (Thymus) and Menthapiperita (Carvacrol). These essential oils and their different doses or combinations in alfalfa silage could be used to improve the performance of ruminants. Moreover, essential oils may act at different levels in energy and protein metabolic pathways, therefore their careful selection and combination may be a useful tool to effectively manipulate rumen fermentation. https://www.biotech-asia.org/vol14no1/effect-of-essential-plant-oil-used-as-an-additive-to-alter-silage-fermentation-in-ruminant-by-in-vitro/ Essential Oils;  InVitro MenthaPiperita; Thyme;