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.