Effects of Yeast Autolysate in the Practical Diet on the Growth Performance, Immune Response, and Disease Resistance of Pacific White Shrimp

The present study was conducted to investigate the effects of supplementing the practical diet with yeast autolysate (YA) on the growth performance, immunity, and disease resistance of Pacific white shrimp Litopenaeus vannamei. Four isonitrogenous and isolipidic practical diets were formulated. The relatively high-fish-meal control diet contained 25% fish meal without YA supplementation (E1). The other control diet contained 20% fish meal without YA (E2). With the E2 diet as the basis, two additional experimental diets were created by further supplementation with 1% YA (E3) and 2% YA (E4). The shrimp (initial weight: 0.30 ± 0.02 g) were fed with the four experimental diets for 8 weeks and then challenged with Vibrio parahaemolyticus. The results indicated that there were no significant differences in survival rate (SR) or feed intake (FI) among these groups. The weight gain rate (WGR) of group E1 was not significantly different from that of groups E3 and E4. The feed conversion ratio (FCR) in group E4 was lower than that of group E2, and group E4 had the highest protein efficiency ratio (PER). The total hemocyte counts (THC) and lysozyme activities in group E3 and group E4 were significantly higher than those of the other groups. Group E3 had the highest respiratory burst (RB). After V. parahaemolyticus administration, group E3 and group E4 had significantly lower cumulative mortalities than group E1 did. In conclusion, the 20% fish meal diet without YA supplementation (E2) yielded a significantly lower growth rate than the 25% fish meal diet without YA supplementation (E1) did. Furthermore, the Pacific white shrimp that received dietary supplementation with 1% YA demonstrated improved growth rate, immune response, and resistance to the V. parahaemolyticus challenge compared with those that were fed the 20% fish meal diet without YA supplementation (E2).