Dietary fermentable fiber upregulated immune related genes expression, increased innate immune response and resistance of rainbow trout (Oncorhynchus mykiss) against Aeromonas hydrophila

• Limited information is available about fermentable fiber and fish immune response.
• Dietary fermentable fiber up regulates immune related genes (lysozyme & TNFα) expression in rainbow trout.
• Hsp70 gene expression was significantly lower in fermentable fiber fed fish.
• Rainbow trout fed fermentable fiber showed stimulated humeral immune response.
• Disease resistance was remarkably elevated in fermentable fiber fed fish.

This trial was carried out to investigate the effects of dietary administration of Vitacel®, a commercial fermentable fiber, on immune related genes (Lysozyme, TNFα and HSP70) expression, innate immune response and resistance of rainbow trout against Aeromonas hydrophila. 120 healthy rainbow trout (81.65 ± 1.49 g) were distributed in six fiberglass tanks assigned to two treatments. The treatments were feeding rainbow trout with diets supplemented with 0 (control) or 10 g kg−1 Vitacel® for 45 days. The results revealed that administration of fermentable fiber significantly (P < 0.05) upregulated lysozyme and TNFα gene expression. HSP70 gene expression was significantly lower in Vitacel® fed fish at the end of trial (P < 0.05). Furthermore dietary administrations of Vitacel® remarkably elevated rainbow trout innate immune parameters include serum lysozyme, ACH50, bactericidal activity and agglutination antibody titer (P < 0.05). Administration of 10 g kg−1 Vitacel® significantly increased rainbow trout resistance against A. hydrophila (P < 0.05). The results of present study revealed that dietary Vitacel® can upregulates immune related genes expression and elevates innate immune response and disease resistance of rainbow trout.