Modulation of Growth and Immunity in Carp by <em>Hermetia illucens</em> Larvae induced by <em>Aeromonas hydrophila</em>

Abstract

This experiment aimed to investigate the effects of <em>Aeromonas hydrophila</em>-induced treatment of black soldier fly (<em>Hermetia illucens</em>) larvae on the growth performance and immune function of the common carp. <em>Aeromonas hydrophila</em>-induced black soldier fly larvae were sterilized and crushed, four diets were prepared by replacing 0% (control group), 10%, 20% and 30% fishmeal of the ration, respectively, and fed to carp (the mean ± SD weight was 48.51 ± 0.47 g) for 30 d. The results showed: (1) The weight gain rate, specific growth rate, and gene expression levels of GH and IGF-1 of carp in 20% and 30% replacement group were significantly higher than those in control group (P<0.05); (2) The plasma lysozyme content in 30% replacement group was significantly higher than those in control group (P<0.05). The plasma acid phosphatase activity and the expression levels of TLR4 and Myd88 in the 20% and 30% replacement groups were significantly higher than those in the control group (P<0.05). The expression level of TLR2 in all experimental groups were significantly higher than those in control group (P<0.05); (3) The numbers of <em>Escherichia coli</em> and Salmonella in the experimental groups were lower than those in control group (P<0.05), while the numbers of Lactobacillus and Bifidobacterium were significantly higher than those in control group (P<0.05). These results suggest that feeding carp with <em>Aeromonas hydrophila</em>-induced larvae of black soldier fly, instead of 10 to 30% fish meal, can significantly enhance their immune capacity and promote growth.