Methods for the chemical analysis of toxic plant substances in the rumen of ruminants are of importance for the diagnosis of intoxications with poisonous plants. The present work establishes a method to estimate components of the essential oil of thuja (thuja orientalis, cupressaceae)in these types of samples. Alpha-Thujone is with 50-60% in the essential oil the main compound and is regarded as the toxic principle.
In order to simulate the situation of a natural digestion, the Rusitec system (rumen-simulation-technique)was used. Chopped twigs of thuja were subjected to rumen fluid in a closed container with an overflow device.
The flow of saliva was simulated by the continuous addition of a bufer solution. After 24 and 48 hours the overflow, and after 48 hours the remaining liquid fraction of the rumen fluid in the container was taken for analysis. The essential oil was extracted with hexane and concentrated. A quantitative determination was done by capillary gas chromatography.
In the various fractions an average recovery of the essential oil from the thuja added at the beginning 2,3% for alpha-thujone, 1,8% for beta-thujone, 6,3% for fenchone and 9,2% for camphor could be achieved.
The observation that the thujones were recovered to a lesser extent than other oil components is an evidence for their fast decomposition in the rumen fluid. Under these circumstances the calculated detection limit is about 100-200 g thuja twigs in the rumen of a cow.
Finally guidelines for sampling rumen fluid were established.
Essential oil / Chemical diagnosis / Poisonous plants / Thuja / Thuja orientalis / Rumen fluid / Rusitec