Pomegranate (Punica granatum) peel extract supplementation in diet influences growth performance, haemato-immunological responses and cytokine expression in pathogen- aggravated Labeo rohita fingerlings

Pomegranate peel extract (PPE) has been widely identified as a rich source of therapeutically active phyto-compounds, known for their beneficial effects in aquaculturable species. In this context, a 60-day feeding trial was carried out to evaluate the effect of supplementation of pomegranate peel extract (PPE) on growth performance, haemato-immunological responses and cytokine gene expression in Labeo rohita (rohu) fingerlings challenged with Aeromonas hydrophila. A total of 240 rohu fingerlings (3.25 ± 0.52 g) were randomly distributed into four treatment groups in triplicates with 15 fish per tank. The groups were fed with four different diets containing graded levels of PPE viz., 0 (control), 0.5, 1.0 and 1.5%. The results demonstrated significantly enhanced weight gain% and specific growth rate (SGR) in the group fed with 0.5% of dietary PPE. The cumulative survival post challenge to A. hydrophila was enhanced to 72.90% in 0.5% PPE fed group as compared to 20.01% in the control group. Haemato-immunological parameters in terms of respiratory burst activity (NBT), serum total protein, globulin and lysozyme activity displayed highest levels in L. rohita fed with the 0.5% PPE diet. Further, the dietary group supplemented with PPE at 0.5% level exhibited upregulated mRNA transcript levels of pro-inflammatory cytokines viz. IL-1β, TNF-α in different lymphoid organs such as gut, kidney and liver of L. rohita fingerlings post-challenge. In contrast, anti-inflammatory cytokine IL-10, was significantly down-regulated in infected rohu fed with 0.5% PPE. Taken together, the best optimum dosage or inclusion level at 0.5% PPE, obtained through the study, represented remarkable favourable variations in growth, haemato-immunological parameters and cytokine gene expression of L. rohita fingerlings. Thus, the dietary supplementation of PPE at 0.5% could effectively enhance different aspects of innate immunity alongwith disease resistance to A. hydrophila infection in L. rohita fingerlings.