The consumption of plants rich in plant secondary metabolites has been associated with improved resilience of parasitised hosts, i.e. their ability to perform under parasitic infection, compared to animals fed conventional feeds (Athanasiadou et al., 2007). Furthermore, such bio-active plants can improve host resistance, which refers to the host ability to regulate gastrointestinal nematode establishment, development, fecundity and survival (Athanasiadou et. al. 2008). Chichorium intybus L. (chicory) is such a bio-active forage and its potential anthelmintic activity is currently investigated as an alternative means to control parasitism in sheep production systems. In the present study we employed an in vitro assay to study a possible mechanism of anti-parasitic action arising from chicory, and to test whether this anthelmintic activity is affected by the vegetative stage of the plant.