Adverse reactions after orange essential oil administration to lambs

Abstract

The major compound in orange essential oil (OEO) is limonene, which has in vitro anthelmintic properties; however, a safe in vivo dose has not been defined for animals. Therefore, a pilot study was conducted to evaluate the effect of an OEO formulation for the control of gastrointestinal nematodes in sheep and to investigate adverse reactions in lambs after OEO administration. A total of 17 lambs received an oral OEO formulation at a concentration of 600mg/mL, in doses of 200, 300, and 600mg/kg. The most common clinical signs observed were head shaking (88.8%), backward head movement (51.1%), and ataxia (74.4%). Lambs treated with 600mg/kg of OEO showed more severe combined clinical signs and longer duration of symptoms, presenting adverse reactions for up to 2h after OEO administration. Testing of different doses and formulations with slower release of the active ingredient is recommended to minimize or eliminate these effects.