RESUMEN
Propolis, a resinous substance collected by Apis mellifera bees from various plant sources is transformed in the presence of bee enzymes. Short- and long-term effects of diet supplementation with ethanol extract of Iranian propolis [EEIP] was investigated on growth and immunity in juvenile rainbow trout. The fish [mean body weight 30 +/- 3.2 g] were fed a commercial diet supplemented with 0 [control], 1, 2 and 5 g/kg EEIP for 96 h and 0, 0.5, 1 and 2 g/kg EEIP for a 45-days. Rainbow trout growth performance significantly [P<0.05] increased by the dietary supplementation of Iranian propolis. Our results showed that significant increase in serum lysozyme activity, complement activity and total immunoglobulin were seen in all treatment groups during short- and longterm feeding trial when compared to the control group. On the basis of our findings, propolis improved rainbow trout growth performance and some immune parameters. Key words: Rainbow trout, Iranian propolis, Growth performance, Immunity