Potential role of dietary white poplar (Populus alba L.) in stimulating growth, digestion, and antioxidant/immune status of Nile tilapia (Oreochromis niloticus)

Abstract The potential use of feed supplements as immune-stimulant and growth-promoting agents in fish diets has drawn a lot of attention. The current research investigated the effects of feeding Nile tilapia (Oreochromis niloticus) on white poplar (Populus alba L.) leaves powder (WP) as a dietary supplement on the growth, digestive functions, and immne-antioxidant parameters. In addition, the fish resistance against Aeromonas sobria challenge was investigated. For 60 days, fish (n = 160; 34.61 ± 0.16 g) were divided equally into four groups, each had four replicates. Fish were fed on diets supplemented with varying levels of WP; 0 g/kg (WP0), 2 g/kg (WP2), 4 g/kg (WP4), and 6 g/kg (WP6), where WP0 was the control diet. The results revealed that WP diets (2–6 g/kg level) substantially boosted the growth (final body weight, weight gain, and specific growth rate %, with improvement of the feed conversion ratio) of Nile tilapia. WP diets improved the amylase (4–6 g/kg level) and lipase (2–6 g/kg level) activity and the intestinal morphometric measures (2–6 g/kg level). WP diets increased the growth hormone (4–6 g/kg level) and reduced leptin hormone and glucose levels (2–6 g/kg level). The immune-antioxidant indices (total protein, albumin, globulin, complement 3, lysozymes, nitric oxide, total antioxidant capacity, glutathione peroxidase, and catalase) were significantly improved by WP diets (2–6 g/kg level). The survival % of fish was improved in a level dependent manner (2–6 g/kg level) compared to the control (WP0) during the A. sobria challenge. Noteworthy, WP diets especially at a level of 6g/kg could be used as a feed supplement for improving the health, growth, immune-antioxidant functions, and disease resistance of Nile tilapia.