The current study estimated the immunotoxicological effects of the herbicide chlorpyrifos at sub-lethal concentration and the potential ameliorative effects of galactooligosaccharide (GOS) in Danio rerio. Fish was sampled after a 56-days feeding with GOS and then exposed to 15 mg/l chlorpyrifos for 7-days to assess the non-specific immune responses (total protein, immunoglobulin and ALP activity). The results revealed that feeding zebrafish with 1% dietary GOS increased total protein levels (P<0.05), but no significant effect was noticed between groups fed 0.5 and 2% GOS and control (P>0.05). There were significant difference between total immunoglobulin levels 1% and control group (P<0.05). Furthermore, in case of ALP activity no significant alteration was noticed between GOS fed fish and control (P>0.05). The present findings revealed that dietary supplementation with GOS could be useful for modulation of the immunity in response to chlorpyrifos exposure, thereby presenting a promising feed additive in aquaculture
