Propolis is a resin-like mixture produced by bees and composed of natural substances demonstrating a broad range of biological activity, e.g. antibacterial, anti-inflammatory, anti-oxidizing, immunostimulating and immunomodulating effects. Among abundant research on its properties has been carried out but a few reports concerning the use of this substance in animal production, particularly in poultry breeding are available. There is little information about its effects upon the morphology of individual organs and tissues predisposed to damage as a result of intensive fattening of poultry. A-day old 400 chicks were divided into equal four groups. Group 1 and 2 served as negative and positive control, respectively. Group 3 and 4 were kept on propolis (10 and 50 mg/kg of feed) supplemented feed for 42 days, respectively. At the end, randomly selected 12 birds from each group were killed humanly. Gross lesions were noted and liver and kidney samples were processed for histopathological studies. The results demonstrated a protective effect of propolis particularly upon the liver of broiler chickens, in which it reduced the intensity of regressive lesions. This protective effect was noticeable especially in the group of birds receiving a higher dose of propolis
