ESTAQUA as a substitute for fishmeal of Litopenaeus vannamei's diet
A feeding trial was carried out to investigate the effects of ESTAQUA (yeast culture with higher crude protein) on the growth performance, hematological parameters, non-specific immunity and disease resistance of Litopenaeus vannamei.
Four isonitrogenous and isolipidic diets were prepared by adding 0, 2.5%, 5.0% and 7.5% yeast culture in a basal diet (Y0,Y2.5, Y5.0 and Y7.5 respectively), substituted fish meal ratio was 0%,10%, 20% and 30%,respectively. Healthy shrimp (initial average weight 0.70±0.03 g) were fed with the diets for 56 days, and the performance, hematological parameters, immunity index were determined. Then,shrimp were challenged by Vibrio harveyi for 7 d, and accumulative mortality rate of the shrimp were calculated.
The results showed that there was no significant difference in the weight gain rate and specific growth rate among the Y2.5, Y5.0 and Y0 groups . The feeding rate in Y5.0 group was significantly higher than that of in Y0 and Y2.5 groups . The content of serum triglyceride in the Y5.0 group was significantly lower than that in Y0 group .The activity of serum glutamic-pyruvic transaminase in Y7.5 group was significantly higher than that of the Y0 and Y2.5 groups , but the content of serum total cholesterol in the Y7.5 group was significantly lower than that in the Y0 and Y2.5 groups. The activity of superoxide dismutase and peroxidase in the liver of shrimp before challenge could be significantly improved by using the yeast culture substituting for 20% and 30% fish meal . The contents of malondialdehyde in the hepatopancreas of shrimp fed with Y7.5 diet were significantly lower than those of shrimp fed with Y0 group. Shrimps were challenged by Vibrio harveyi for the 7 days after the breeding experiment, the cumulative mortality rate of Y7.5 group was significantly lower than that of Y0 group .
It is indicated that there is no significant difference on the growth performance of shrimp while the proportion of ESTAQUA as a substitute for fishmeal was less than 20%. But the replacement proportion up to 30% can significantly improve the nonspecific immunity and disease resistance of L. vannamei.