The plant extracts offer the possibility for an alternative, sustainable, non-medicinal treatment approach for worm infections. Furthermore, the goal is to market the extracts as a feed additive that will increase both the production and general health and welfare of the nimals. Our strategy is, as a first step, to target organic egg layers. Due to new EU regulations on increased withdrawal time ollowing antiparasitic treatment, there is an urgent need for novel strategies in organic egg-laying hens suffering from parasite infections. The plant extracts contain either enzymes (proteases) that degrade the parasite cuticula and their eggs, or other ubstances that paralyze the parasites and lead to their expulsion. The effect of some of the compounds has been demonstrated in vitro and in vivo and showed that they kill not only the most common intestinal worm Ascaridia galli but also other important worms like Heterakis gallinarum and Capillaria spp; other compounds have not been tested in live hens yet but showed promising results in vitro. To explore and substantiate the antiparasitic effects of these plant extracts, the following activities are proposed: Development of an in vitro method for screening of bioactive compounds as well as quality assurance of plant extracts incl. minimizing batch variation 2. Experimental investigation of the effect of the compounds on worm infections in (a) experimentally infected and (b) naturally infected organic egg laying hens 3. Clinical tests under field conditions to (a) substantiate the effect of the novel formulation regarding palatability, administration method and dose and (b) efficacy using a 5-day administration scheme or continuous in-feed supplementation in organic flocks 4. Achieve market authorization in Denmark and the EU incl. screening of potential for local production of organic plants 5. Stakeholder involvement and dissemination activities.The project aims to develop feed additives that can efficiently treat parasitic worms with one or more plant extracts, thus avoiding the withdrawal period as well as use of conventional medicine, saving eggs and money for organic producers, improving feed utilization, while improving animal welfare in organic egg layers. www.orgprints.org