[Essential oils for the nutrition of poultry, swine and ruminants].

Essential oils are very complex mixtures of volatile, lipophilic compounds originating from plants. Due to their lipophility they posses a good intestinale and percutane absorption. Under external application essential oils demonstrate antiphlogistic or rubefacient to pro-inflammatority activities. Orally intake they stimulate the secretion of digestive enzymes and increase gastric and intestinal motility. Moreover they show spasmolytic, expectorative and diuretic activities. Besides antimicrobial properties on bacteria and fungi have been observed in vitro and in vivo. Due to their various effects essential oils increasingly gain attention in animal nutrition and are discussed to be alternatives to antibiotic growth promoters. In some studies essential oils have been reported to reduce intestinal pathogens in broilers and piglets. When administered to ruminants essential oils decrease ruminal ammonia production by suppression the growth of deaminative microorganisms. However, the observed effects on growth performance are inconsistent among studies. In conclusion, there are still some unanswered questions concerning the mode of action, metabolic pathway and optimal dosage of essential oils in different animal species. Further scientific research is therefore needed to use essential oils effectivly in livestock feeding.