Under organic regulations, farmers in the uk are allowed to drench periparturient ewes with an anthelmintic drug before returning them to pasture. Although such practice is against the principles of organic farming, it is allowed as it reduces parasite contamination of the pastures and consequently reduces the risk of parasitism in growing lambs. Alternatives to control parasitism, which do not jeopardise the health and welfare of grazing ruminants and also minimise anthelmintic input in organic systems are currently being investigated. Grazing bioactive forages, such as chicory has resulted in a lower level of parasitism than sheep grazing on grass/clover pastures (Marley et al, 2003). The objective of this experiment was to investigate whether grazing on chicory can affect the epidemiology of gastrointestinal parasitism, so that control of sub-clinical parasitism could be achieved without the use of anthelmintics.