This thesis presents a review of the appropriate literature and results from the experiments that were conducted with water-soluble carbohydrate extracts from four Australian and New Zealand plants, 'Arthropodium cirratum' (Rengarenga lily), 'Cordyline australis' (Cabbage tree), 'Acacia pycnantha' ('Acacia' or Golden wattle) and the seaweed, 'Undaria pinnatifida' ('Undaria' spp. or Wakame). Plant extracts and commercially available prebiotic compounds, with a chemical composition of which was similar to that of the plant extracts were examined for their use as alternatives to antibiotic growth promoters (AGPs) in broiler chickens. ... The implications and significance of the major findings and an overview of effects of the studied plant extracts and prebiotic compounds, as alternatives for AGPs, on growth performance and health of broiler chickens are discussed. The major highlights of each experiment are presented in the relevant chapter in form of an abstract.