Growth and immunomodulation in individually reared giant freshwater prawn, Macrobrachium rosenbergii (de man 1879) as a function of dietary chitosan extracted from black soldier fly (

Abstract

Macrobrachium rosenbergii is one of the major species produced in world aquaculture. Functional feed additives can contribute to the sustainable production of prawns, and chitosan is one of the additives, which is widely used for various applications, including improving growth and immunity in aquatic species. One of the sources, black soldier fly larvae (BSFL) grown on organic wastes, is a sustainable source of chitosan with year‐round availability. The present study evaluates the growth and immune‐enhancing abilities of chitosan from two sources: shrimp shell chitosan, procured commercially, and BSFL chitosan, extracted in our laboratory, at two different dietary concentrations in Malaysian giant prawn ( Macrobrachium rosenbergii ). In the 90‐day feeding trial, five dietary treatments were tested, wherein prawns housed in individual sections were fed isonitrogenous diets: Diet 1 (0 chitosan), Diet 2 (2 g/kg shrimp shell chitosan), Diet 3 (4 g/kg shrimp shell chitosan), Diet 4 (2 g/kg BSFL chitosan), and Diet 5 (4 g/kg BSFL chitosan). The water stability of diets ranged between 28.65% and 32.33% weight loss at 1024 min, with Diet 4 being significantly less stable than other diets. However, variations in the water stability of diets did not influence the water quality and growth performance. At the end of the growth trial, prawns fed Diet 3 and Diet 5 displayed significantly higher weight gain (457.64% and 472.54%), specific growth rate (0.82% and 0.83%/day), and condition factor (1.07 and 1.08). The prawns fed a chitosan‐containing diet had a lower feed conversion ratio than those fed a control diet, ranging between 1.06 and 1.47. The prawns had a mean molt frequency of 5.56 ± 0.07, and prawns fed the Diet 5 treatment displayed higher fourth and fifth molt weight increments of 35.08% ± 2.20% and 25.75% ± 1.81%, respectively, and also showed a higher wet tail muscle index of 41.42%. The apparent digestibility of dry matter of 85% was obtained by the prawns fed 4 g/kg dietary chitosan. The expression profiling of antioxidant and immune‐related genes, namely sod , cat , proPO , peroxinectin , and crustin were significantly upregulated in chitosan‐containing treatments. In conclusion, a 4 g/kg dietary chitosan level results in higher growth and immunity in prawns compared to a 2 g/kg dietary chitosan level. Furthermore, BSFL‐derived dietary chitosan performs similarly to shrimp shell (commercial) chitosan as a functional feed additive.