Effects of dietary defatted Periplaneta americana meal on the growth, antioxidant status, immunity, hepatic and intestinal health of Nile tilapia
This study estimated the effects of replacing fish meal (FM) with defatted Periplaneta americana meal (PAM) on the growth, antioxidant status, immunity, and hepatic and intestinal health of juvenile Nile tilapia (Oreochromis niloticus). Five diets were formulated by replacing 0% (PAM0), 25% (PAM25), 50% (PAM50), 75% (PAM75), and 100% (PAM100) of FM, and then fed to triplicate groups of 15 fish (10.58 ± 0.73 g) for 60 days. The results indicated that growth and feed utilisation were increased in the PAM25 group while decreased in the PAM100 group (P < 0.05). The PAM diets positively influenced serum biochemical parameters. Furthermore, the PAM25 diet enhanced the intestinal protease activity compared to the PAM0 diet (P < 0.05), ameliorating the hepatic and intestinal morphology. In terms of gene expression, PAM25 diet increased the expression levels of growth hormone and growth hormone receptor (P < 0.05) compared to the PAM0 diet. The expression of antioxidant genes was enhanced in the liver and intestine in fish fed PAM25, PAM50, and/or PAM75 diets. The intestinal caspase-3 expression was downregulated (PAM25), while the caspase-9 expression was upregulated in the liver and intestine (PAM75 and PAM100) (P < 0.05). The PAM diets also decreased the expression of pro-inflammatory factor genes, including interleukin-1β (IL-1β) (PAM25 and PAM50) in the liver and IL-1β (PAM25) and interleukin-8 (PAM50) in the head kidney, and increased the expression of anti-inflammatory factor genes such as tumor necrosis factor-α (PAM25) in the liver and head kidney and interleukin-10 (IL-10) (PAM25 and PAM50) in the head kidney (P < 0.05). Overall, these results demonstrated that about 31% replacement of FM (31.58% and 31.93%) with PAM resulted in the best growth performance; However, the FM replacement above 50% declined growth, antioxidant capability, immunity, and hepatic and intestinal health of Nile tilapia.