Simple SummaryStrategies to reduce the amount of marine ingredients in the diet of commercially important species such as whiteleg shrimp have received great attention. Yeast products obtained fromSaccharomyces cerevisiaeare a rich source of protein, amino acids and energy. Furthermore, yeast is a abundant source of nucleotides, beta-glucans, mannan oligosaccharides, chitin and peptides that have shown to improve immune response, growth performance and stress resistance in shrimp. The results of the present study showed that supplementing 4% of hydrolyzed yeast in shrimp diet with low fishmeal (10%) could improve growth, intestinal morphology and disease resistance.AbstractAn eight-week feeding trial was performed to evaluate the effects of yeast hydrolysate (YH) supplementation in a low-fishmeal diet on the growth, immune responses, intestinal histology and disease resistance of whiteleg shrimp (Litopenaeus vannamei). Five experimental diets were produced by supplementing YH at 0 (CON), 0.5 (YH0.5), 1 (YH1), 2 (YH2) and 4 (YH4) % to a basal diet containing 10% fishmeal and compared with a positive control with 25% fishmeal (FM25). Shrimp with an initial average weight of 0.43 ± 0.005 g (mean ± SD) were stocked in 18 tanks and fed the experimental diets (38% protein and 8% lipid) four times a day. Results showed that shrimp fed the FM25diet exhibited significantly higher final body weight, weight gain, specific growth rate and protein efficiency ratio than those fed CON, YH0.5, YH1and YH2diets (p< 0.05). However, there were no significant differences between shrimp fed the YH4and FM25diets (p> 0.05). In addition, there were no significant differences in whole-body proximate composition, hemolymph biochemical parameters and non-specific immune responses among treatments. Intestinal villi length and muscular layer thickness of shrimp fed the YH4and FM25diets were significantly higher than the other groups. At the end of the bacterial (Vibrio parahaemolyticus) challenge test, shrimp fed YH4and FM25diets showed a significantly higher survival rate than those of shrimp fed CON, YH0.5and YH1(p< 0.05). These results suggest that supplementing 4% YH in diet containing 10% fishmeal could beneficially influence growth, intestinal morphology and disease resistance of whiteleg shrimp.