Effect of dietary prebiotic inulin on growth, body composition and gut microbiota of Asian seabass (Lates calcarifer)

• The beneficial effect of inulin supplementation on growth and FCR has been ascertained in seabass.
• Inulin supplementation altered the gut microbial community of seabass.
• The optimal level of inulin supplementation was found to be 15 g kg−1 in seabass diet.

A feeding trial was conducted to study the effect of inulin on growth, body composition and gut microbiota of Lates calcarifer fingerlings (average weight: 7.14 ± 0.05 g). Inulin was supplemented at five different concentrations 0, 5, 10, 15 and 20 g kg−1 in the diet (400 g kg1 protein and 90 g kg−1 lipid) of L. calcarifer. The results of the 60 days feeding trial revealed that dietary inulin supplementation had a significant effect on specific growth rate (SGR) (linear, P = 0.029; quadratic, P = 0.022) and feed conversion ratio (FCR) (linear, P = 0.033; quadratic, P = 0.003) between control and treatments. However, the final body weight (FBW) (quadratic, P = 0.0138) and weight gain (WG) (quadratic, P = 0.0150) followed a quadratic pattern. Supplementation of inulin did not affect whole body moisture and lipid. However, crude protein increased both linearly (linear, P = 0.001) and quadratically (quadratic, P = 0.001) in fish fed with 20 g kg−1 inulin supplemented diets and a quadratic pattern in ash (P < 0.05) was recorded. Similarly hepatosomatic index (HSI) significantly increased (linear, P = 0.008; quadratic, P = 0.048) in fish fed 15 g kg−1 inulin. Polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) analysis of gut samples from inulin supplemented diet revealed the change in the gut microbial community of Asian seabass. It could therefore be inferred that inulin supplementation is beneficial in the diet of Asian seabass and supplementation at 15 g kg −1 level is optimal for enhancing growth.