Supplementation of Yeast Extract to Practical Diet Improves the Growth, Anti-Oxidative Capacity and Intestinal Morphology of Shrimp Litopenaeus vannamei

Two control diets based on the commercial formula were designed to contain high (27%, D1) and low (22%, D2) levels of fish meal, respectively. Into D2, 500, 1000 and 1500 mg kg−1 of yeast extract were added, respectively, yielding three experimental diets (YE1 through YE3). Shrimp (initial body weight 0.30 g ± 0.02 g) were fed with the experimental diets, five tanks each diet and 30 shrimp individuals each tank, for 8 weeks, and then challenged with Vibrio parahaemolyticus. The results showed that the specific growth rate (SGR) of shrimp in D2 was significantly lower than that of shrimp in D1 (P < 0.05). The SGR of shrimp in YE3 was similar to that of shrimp in D1. The feed intake of shrimp was similar between D1 and D2. The feed conversion ratio and protein efficiency ratio of shrimp were similar among all diets (P > 0.05). YE significantly improved the activity of glutathione S-transferase. The concentration of glutathione (GSH) and the total serum anti-oxidative capacity (T-AOC) of D1 were significantly higher than those of shrimp feeding other diets (P < 0.05). The content of serum malondialdehyde of shrimp feeding YE2 and YE3 was significantly lower than that of shrimp feeding D2 (P < 0.05). The thickness of intestine muscular layer of shrimp feeding YE1 and YE2 was similar to that of shrimp feeding D1. The shrimp feeding YE1 showed the highest villus height of intestine among all groups. The cumulative mortality after challenging was similar among all groups (70.00%–86.67%) (P > 0.05). In conclusion, 1000–1500 mg kg−1 of YE was suggested to be supplemented into the practical diets to improve the growth, anti-oxidative capacity and intestinal morphology of shrimp L. vannamei.