Dietary supplementation of thyme essential oil in broiler chickens

Beneficial influence of herbal products and phytogenic feed additives on animal health and performance is an actual topic for the worldwide research. Phytogenic feed additives contain a high number of bioactive plant compounds and each of them can specifically influence an animal organism. However, information about their absorption, mode of action, metabolism and excretion from animal organism was not yet sufficiently ascertained. Our research was focused on dietary supplementation of thyme essential oil (TEO) to broiler chickens and quantification of its main compound (thymol) in duodenal content, duodenal wall, liver and plasma. Since a positive effect of TEO on animal organism was already observed [1], we would like to deeply investigate the relation between thymol concentrations in intestine, liver and plasma. Thirty-two 1-day old broiler chickens (hydrid Ross 308) were randomly allocated into 4 dietary treatments with increasing TEO supplementation (0%; 0.1%; 0.05%; 0.1% (w/w)). Chickens were slaughtered after 4 weeks of supplementation and samples of duodenal content, duodenal wall, liver and plasma were collected. Thymol content in TEO was analysed by the method gas chromatography-mass spectrometry. Thymol derived from TEO was detected in duodenal content, tissues and plasma using solid-phase microextraction followed by gas chromatography coupled to mass spectrometry. Thymol concentrations in duodenal wall, liver and plasma significantly increased with the highest TEO supplementation. Thymol levels were significantly higher in duodenal wall in comparison to thymol levels in liver in all dietary treatments. Moreover, thymol concentrations in the duodenal wall correlated with thymol levels in the liver and plasma. Additionally, thymol amounts in the liver correlated with those in plasma. Our findings indicate a certain relation between thymol absorption and transport along the axis intestine - liver - systemic circulation. According to our results, we could hypothesise that thymol was intestinally absorbed, transported from duodenal wall into liver and subsequently distributed within the body.