Evaluation of corn distillers dried grains with solubles (DDGS) replacement for fishmeal in the diet for juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂)

This experiment was conducted to determine the optimum amount of corn distillers dried grains with solubles (DDGS) in the diet of juvenile hybrid grouper by studying the effect of DDGS on the growth, intestinal morphology, and mRNA expression levels. The diets were formulated with 45% fishmeal (FM) as the control group (D0). Six iso-nitrogenous and iso-lipidic diets were formulated using DDGS to replace 6.67%, 13.33%, 20%, 26.67%, and 33.33% of the FM protein (D1, D2, D3, D4, and D5, respectively). A total of 720 juvenile hybrid groupers with uniform body weight (11.88 ± 0.05 g) were selected from six treatments and four replicates (30 fish each) and farmed for 56 d. No significant effect of DDGS substitution for FM was found on survival rate (SR) and the feed conversion rate (FCR) (P > 0.05), but weight gain rate (WGR) and specific growth rate (SGR) of the control, 6.67%, and 13.33% groups were significantly higher than those of the other groups (P < 0.05). With increasing substitution level, the (amylase) AMS activity in the intestine decreased significantly and was significantly lower in the 20% and 26.67% groups than in the other groups (P < 0.05). The microvilli in the 26.67% and 33.33% groups were severely damaged and had significantly lower intestinal villi height (VH) than in the other groups (P < 0.05). The mRNA levels of anti-inflammatory factors il-10 and tgf-β1 tended to decrease with increasing substitution levels, and the mRNA levels of pro-inflammatory factors tnf-α and il-1β tended to increase with increasing substitution levels. In conclusion, According to the correspondence between DDGS substitution level and WGR, the optimum level of DDGS substitution for fishmeal in the feed was 7.80%, which significantly improved growth performance and intestinal health.