Effect of different dietary zinc sources on seminal plasma enzymatic activity, antioxidant, and immune-related gene expression in rainbow trout (Oncorhynchus mykiss)

The objective of the present work was to survey the effects of different sources of zinc supplements on serum enzymatic activities, the expression of genes related to antioxidant and immunity in rainbow trout (Oncorhynchus mykiss). Male rainbow trout were fed for 16 weeks on a diet supplemented with 40 mg kg−1 of mineral zinc supplement (MZ; ZnSO4·7H2O), 40 mg kg−1 of organic zinc (OZ), 40 mg kg−1 of zinc nanoparticles (NZ), and control diet (CD). After 16 weeks, fish fed different diet revealed significant serum enzymatic activities compared to the control treatment (P < 0.05). The lowest levels of aspartate aminotransferase (AST), alanine transaminase (ALT), lactate dehydrogenase (LDH), and superoxide dismutase (SOD) enzymes were observed in seminal plasma of fish in treatment fed on MZ (P ˂ 0.05). Based on the results, dietary different zinc sources upregulated the gene expressions of Cu/Zn-superoxide dismutase (Cu/Zn-SOD), manganese superoxide dismutase (Mn-SOD) and catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase mu (GST), and nuclear factor erythroid 2-related factor 2 (Nrf2), while the gene expression of glutathione S-transferase (GST) was not significantly modified by MZ and OZ. The MZ and OZ groups significantly (P < 0.05) upregulated the TNF-α transcription in the head kidney tissues when compared with the NZ and CD groups. Meanwhile, the OZ and NZ groups did not change IL-1β mRNA level of the head kidney when compared with the CD group (P > 0.05). The results also indicated that cytokine gene expression, especially TNF-α and Lyz II, may affect fish reproduction. The results revealed that fish fed diet containing mineral zinc and organic zinc supplement showed significantly higher antioxidant and immune response as compared to the control groups (P < 0.05). It is therefore recommended that dietary mineral zinc and organic zinc administration may effectively promote the immune system and antioxidant capacity of rainbow trout.