Impact of transportation in freshwater and brackish water on Oreochromis niloticus (Nile tilapia) resistance

Background Oreochromis niloticus has great economic value and potential for farming and development. Transportation of fish was done for breeding or trading purpose and it is a challenging aspect of aquaculture. This study aimed to investigate the effect of transportation in freshwater and brackish water on the resistance of O. niloticus as well as transportation stress mitigation effect of NaCl. Four equal groups were used; each of 50 fish, the 1st group served as the control (P 1), while the 2nd group (PT 2) was transported in water without salt, the 3rd (PT 3) and 4th (PT 4) groups were transported in water containing 5 gL ^− 1 and 10 gL ^− 1 salt respectively. PT 2, PT 3 and PT 4 were transported for 5 hours without any rest or sedative drugs. Results The serum cortisol of O. niloticus significantly increased at 0 h and then decreased at 12 and 24 h post transportation in the PT 2 group and non significantly increased at all point times in the PT 3 and PT 4 groups comparing to P 1 group. Mucin2 gene expression was non-significantly up regulated in the PT 2 group and down regulated in the PT 3 and PT 4 groups at 0 h comparing with P 1 group, but at 12 and 24 h it was significantly up regulated in the PT 2, PT 3 and PT 4 groups. The β Defensin-1 and 2 genes expression was non-significantly down-regulated in the PT 2 group and significantly up regulated in the PT 3 and PT 4 groups at 0 h., while at 12 and 24 h was significantly down regulated in the PT 2 group and non-significantly down regulated in the PT 3 and PT 4 groups, it significantly down regulated in the PT 2 and PT 3 group and non significantly down regulated in the PT 4 group at 24 h. Non significant up regulation in interleukin − 1β gene expression was reported in the PT 2 group and non significant down regulation in the PT 3 and PT 4 groups at 0 h. However, significant up regulation was recorded in the PT 2, PT 3 and PT 4 groups at 12 and 24 h. The Tumor necrosis factor- alpha gene expression was non-significantly up regulated in the PT 2 group and non-significantly down regulated in the PT 3 and PT 4 groups at 0h. However, it was significantly up regulated in the PT 2, PT 3 and PT 4 groups at 12 and 24 h. Conclusion The results of this study confirmed the stressful effect of transportation on O. niloticus as well as the transportation stress mitigation effect of NaCl.