Dietary sodium propionate enhances growth performance, digestive enzymes, haematology and immunity in <i>Wallago attu</i>

Sodium propionate (SP), a short-chain fatty acid, has been widely used as a feed additive to improve fish growth and health status. The current experiment was designed to investigate the effects of dietary SP on growth, enzymatic activities, haematology and immune status of Wallago attu. Fingerlings (initial weight = 8.80 ± 0.58 g) were fed with graded levels of SP comprising 0.0, 0.5, 1.0, 2.0, 4.0 and 8.0 g/kg levels for 60 days in triplicate glass aquaria (89 × 58 × 61 cm [length × width × depth]). The results showed significant (p < 0.05) improvement in growth parameters such as weight gain (%), specific growth rate and feed conversion ratio up to 4 g/kg SP. Moreover, the whole-body proximate composition (crude protein and lipid content) and antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase) showed significant improvements up to 4 g/kg. However, the digestive enzyme activities (amylase, protease, lipase) increased significantly at 2 g/kg, while decreased malondialdehyde content was observed at 2-4 g/kg. Furthermore, the haematological (haemoglobin, haematocrit, red blood cells and white blood cells counts) and nonspecific immune parameters (serum total protein, lysozyme and IgM) improved significantly up to 4 g/kg and decreased thereafter. Moreover, Polynomial regression analysis showed that 5.88 g/kg SP is the optimum requirement for the growth of W. attu fingerlings when fed with graded levels of SP. In conclusion, the SP supplementation in W. attu showed best results ranged between 2 and 4 g/kg level by improving fish health and growth performance.