Enrichment of common carp (Cyprinus carpio) diet with malic acid: Effects on skin mucosal immunity, antioxidant defence and growth performance

Abstract

The present study investigated possible effects of dietary malic acid on the expression of immunity, antioxidant and growth-related genes expression as well as skin mucus immune parameters in common carp. Common carp (Cyprinus carpio) fingerlings were fed diets supplemented with different levels (0 [control], 0.5%, 1%, 2%) of malic acid (MA) for 60 days. The results revealed highest expression levels of immune-related genes (TNF-alpha, il1b, il8 and lyz) in skin of common carp fed 2% MA (P<0.05). Regarding 1% MA treatment comparison with control group, significant difference was noticed just in case of lyz (P<0.05). Evaluation of growth-related genes expression revealed no significant difference between treatments (P>0.05). The study of antioxidant-related genes (gsta and gpx) in the skin of common carp fed with MA, showed significant difference between treated groups and control (P<0.05). Carps fed with 2% MA had highest alkaline phosphatase activity in skin mucus compared to other treated groups and control (P<0.05). There were no significant differences between 0.5% and 1% and control (P>0.05). The study of total protein and total immunoglobulin (Ig) in common carp skin mucus revealed no alteration following MA treatment (P>0.05). The present data demonstrated that feeding with MA altered immune and antioxidant genes expression in skin mucus of common carp.