Effects of dietary reishi mushroom (Ganoderma lucidum) on the growth performance of Nile tilapia, Oreochromis niloticus juveniles

Abstract

In aquaculture, several medicinal mushrooms have been successfully used as prebiotics, with attractive growth-stimulant, immune-modulatory, and antioxidant functions for several finfish species. Herein, we designed a 90-day continuous feeding trial to assess the impacts of supplementing diets with a reishi mushroom (Ganoderma lucidum) powder on growth parameters and expression responses of some genes that correlated with growth, digestion, and lipid metabolism in Nile tilapia. Four isonitrogenous and isocaloric diets have been formulated by incorporating reishi mushroom powder (RMP) at varying inclusion doses as 0.0, 5.0, 10.0, and 20.0 g/kg to form four RMP-based diets defined as RMP0 (reference diet), RMP5, RMP10, and RMP20, respectively. After the end of the 90-day feeding experimental trial, mean final weight (Wt90), weight gain percentage (WG%), feed conversion rate (FCR), and specific growth rate (SGR) have been improved significantly in fish groups fed RMP-based diets with regard to those fed the reference diet. The highest Wt90, WG%, and SGR values and the lowest FCR values were present in RMP10 group in comparison with the other groups. However, no significant variations were found in these parameters between RMP5 and RMP20 groups. The fish survival rate (SR %) was the same between all test groups. At the molecular levels, the expression levels of growth-correlated genes such as growth hormone, growth hormone receptor, and insulin growth factor 1 have been increased in the RMP10 group. Similarly, the mRNA transcripts of digestion-correlated genes such as pepsinogen, chymotrypsinogen, trypsinogen, and cholecystokinin genes, and lipid metabolism-related gene (lipoprotein lipase) have been up-regulated significantly in the RMP10 group. Of interest, the second-order polynomial regression performed on Wt90, WG%, SGR, and FCR values against the dietary RMP levels showed that the optimum supplementation level of RMP in diets of Nile tilapia was 12.50 g RMP / kg diet. Our findings propose the noticeable prebiotic effects of RMP for improving aquafeed's functionality and tilapia culture's sustainability.