In the last decade the scientific interest on the use of herbs as phytogenic feed additives increased enormously. The present work establishes and compares three extraction methods for nineteen monoterpene components of essential oils with or without incubation wiht rumen content. In various series of experiments the monoterpenes were incubated with McDougall buffer solution, which simulated saliva, and with fresh rumen content, which was obtained from a cow with an implanted rumen fistula. The extraction techniques were liquid-liquid extraction, solid phase extraction (SPE) and solid phase microextraction (SPME). The patterns of volatile components were recorded by gas chromatography/mass spectrometry.
The results show, that after 24 hour incubation only few substances, the alcohol-monoterpenes menthol, thymol, carvacrol and fenchol and the ketones menthone, fenchone and camphor were recovered to an extent of 33-79 %. These are the substances which are recommended for further studies.