Effect of essential oils on ruminal fermentation: A review

Microbial digestion in the rumen is a complex phenomenon that efficiency can be improved by the use of food additives. The use of natural additives in ruminants can act on the balance of the ruminal population, and fermentation is directed towards the formation of end products that must be used more efficiently by the animal. Flora regulators, which are antibiotic in nature, have been widely used, but their use is now prohibited in livestock farming because of their harmful effect on public health. An alternative is to use natural product like essential oil whose antibacterial activity and effect on ruminal fermentation has been demonstrated. These are mixtures of lipophilic, liquid and volatile products present in higher plants used for their antiseptic and antibacterial properties over a broad bacterial spectrum. Antibacterial activity appears to result from a combination of several modes of action, involving different cellular targets and depends on several parameters such as the type of microorganisms tested, the composition of the EO and the method used. Use of essential oils (EOs) to modulate rumen microbial fermentation process to improve feed utilization efficiency and decreasing methane emission. This review explores the informations available in the literature regarding EO and their majority components and their mode of action, antimicrobial activity on rumen fermentation and methane reduction.