DietaryPeriplaneta americana extract improved the growth performance, immune, and antioxidative status, and crowding stress responses in Nile tilapia

The objective of this study was to assess the beneficial effects of dietary Periplaneta americana extract (PAE) supplementation on growth performance, immune, and antioxidative status, liver health, and crowding stress responses in Nile tilapia ( Oreochromis niloticus ). The fish (initial weight 55.01±1.73 g) were fed with one of the four diets containing PAE (0, 1, 2 and 4%) for 60 days followed by a 3-h crowding stress trial. PAE enhanced the weight gain rate at concentrations of 2 and 4% and lowered the feed conversion rate at 4% ( P <0.05), which possibly due to the increased activities of intestinal protease and amylase ( P <0.05). Dietary PAE supplementation at 2 and 4% increased levels of total protein and albumin, while PAE at 4% increased complement C3 and C4 levels ( P <0.05). Dietary PAE supplementation also enhanced serum lysozyme activity at all concentrations tested ( P <0.05). Fish fed with 2 and 4% PAE exhibited lower activities of serum enzymes, including alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase ( P <0.05). Dietary PAE supplementation at 2 and 4% significantly decreased malondialdehyde and increased levels of superoxide dismutase, catalase and glutathione. In addition, PAE demonstrated hypolipidemic and hypocholesterolemic effects, as reflected by lower serum levels of total cholesterol, triglycerides, and higher density lipoprotein cholesterol in the 1-4% groups compared to the 0% group. Crowding stress affected serum cortisol and glucose levels in all treatments ( P <0.05), but PAE supplementation alleviated increase in the serum cortisol and glucose after stress trial ( P <0.05). In conclusion, PAE has the potential to enhance growth performance, improve the intestinal enzyme activities and immune and antioxidative status, alleviating the negative effects of crowding stress in Nile tilapia juveniles. The recommended dietary levels of PAE were 20-40 g/kg for Nile tilapia.