At the end of the study the innate
immune responses (Ig levels, lysozyme activity and ACH50) were significantly higher in 2% and 3% FOS
fed fish (P < 0.05), whereas, 1% dietary FOS only elevated serum lysozyme activity. All dietary FOS levels
significantly increased resistance to a salinity stress challenge (P < 0.05) and highest survival was
observed in the 3% FOS group. Similarly, digestive enzyme activities were significantly elevated with
increasing levels of dietary FOS (P < 0.05). Subsequently, elevated growth performance (final weight, SGR
and FCR) was observed in roach fed 2% and 3% FOS compared to the control group (P < 0.05). These
results indicate that FOS can be considered as a beneficial dietary supplement for improving the immune
response, stress resistance, digestive enzyme activities and growth performance of Caspian roach fry.