Dietary Supplemented Pomegranate Peel Ethanolic Extract Improves Growth, IGF-1 Expression and Immune Responses in Labeo Rohita Fingerlings Reared in Varying Stocking Densities

Pomegranate peel waste was collected and converted to peel extract using five different solvents and the quantitative and qualitative assessment of antioxidant activities of the extract were carried out. From the results, it was observed that pomegranate peel ethanolic extract (PPEE) showed highest dry matter recovery and antioxidant activity. Following a 3 × 3 factorial design, four hundred and five (4.36—4.45 g) fingerlings were stocked in three different stocking densities (10,15 and 20 nos / 75L). Three isonitrogenous (30%) and isocaloric (345 kcal DE/100 g) practical diets were prepared using different PPEE levels (0, 0.5, and 1%), in triplicates. Results showed that high stocking density reduced the weight gain (WG), weight gain % (WG %), IGF-1 gene expression, feed efficiency ratio (FER), and protein efficiency ratio (PER) significantly (p < 0.05) in fish, while diet containing PPEE extract at 1% indicated improvement in growth and feed utilisation parameters irrespective of stocking density. All the antioxidant parameters except glutathione and glucose-6-phosphate dehydrogenase (G6PDH) were significantly (p < 0.05) increased in high stocking density groups. Blood glucose and hepatic glycogen content followed an inverse trend with high stocking density as well as PPEE supplementation. High and medium stocking density groups showed a lower immune response, while all the PPEE (0.5 & 1%) fed groups showed increased value and compared to their respective control groups. Consequently, it can be concluded that pomegranate peel waste can be valorised as a growth promoting and immunomodulatory nutraceutical for Labeo rohita.