Evaluation of Yeast Hydrolysate in a Low-Fishmeal Diet for Whiteleg Shrimp ( Litopenaeus vannamei ).

An 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 (YH 0.5 ), 1 (YH 1 ), 2 (YH 2 ) and 4 (YH 4 ) % to a basal diet containing 10% fishmeal and compared with a positive control with 25% fishmeal (FM 25 ). 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 FM 25 diet exhibited significantly higher final body weight, weight gain, specific growth rate and protein efficiency ratio than those fed CON, YH 0.5 , YH 1 and YH 2 diets ( p < 0.05). However, there were no significant differences between shrimp fed the YH 4 and FM 25 diets ( 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 YH 4 and FM 25 diets were significantly higher than the other groups. At the end of the bacterial ( Vibrio parahaemolyticus ) challenge test, shrimp fed YH 4 and FM 25 diets showed a significantly higher survival rate than those of shrimp fed CON, YH 0.5 and YH 1 ( 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.