Exogenous protease supplementation in high- and low-fishmeal diets for Pacific white shrimp (Penaeus vannamei): Comparative effect on growth, immunity, nutrient digestibility and gut health
Mirasha Hasanthi, Rutchanee Chotikachinda, Nalin Medagoda, Kyeong‐Jun Lee
Abstract
The present study evaluated the effects of exogenous protease supplementation in low- and high-fishmeal (FM) diets on growth performance, feed utilization, innate immunity, digestive enzyme activity, nutrient digestibility, gut microbiota and intestinal morphology of Pacific white shrimp ( Penaeus vannamei ). A 2 × 3 factorial experiment was designed with two dietary FM levels (200 g/kg, positive control [PC]; and 100 g/kg, negative control [NC]) and three protease levels (0, 400 and 800 mg/kg) to obtain six experimental diets designated as PC, PC400, PC800, NC, NC400 and NC800. Six replicate groups of 30 shrimp (initial weight 0.3 ± 0.0 g) were fed the diets for 8 wk. Protease supplementation significantly improved ( P < 0.05) growth performance and feed utilization efficiency in both high- and low-FM diets. Innate immunity and antioxidant enzyme activities were significantly enhanced ( P < 0.05) with increasing FM and protease levels. Furthermore, the inclusion of protease in low-FM diets significantly increased ( P < 0.05) total hemocyte count and phagocytic, phenoloxidase, lysozyme and superoxide dismutase activities, reaching levels comparable to the PC group. Increasing FM and protease levels significantly upregulated the expression of proPO , crustin, TGF-β , IKK-β and TLR3 genes, while downregulating TNF-α . The inclusion of protease in the low FM diet significantly increased ( P < 0.05) digestive enzyme activities, intestinal villi length, whole-body amino acid composition and nutrient digestibility to the levels comparable to the PC group. The relative abundance of heterotrophic marine bacteria, Gram-positive bacteria and Lactobacilli spp. in the gut significantly increased ( P < 0.05) with increasing protease levels, while an inverse relationship was observed for Vibrio spp. These results demonstrated that protease supplementation in either the high- or low-FM diets could improve shrimp growth, feed utilization efficiency, immunity, nutrient digestibility, intestinal morphology and gut microbiome. Notably, supplementing the low-FM diet with 800 mg/kg protease improved shrimp performance, reaching levels comparable to those obtained with the PC diet.