Dietary Quillaja saponin improves growth and resistance against acute hyposalinity shock in the black tiger shrimp Penaeus monodon post larvae

Abstract

Acute hyposalinity stress in shrimp ponds is a natural occurrence during the rainy season and the provision of functional ingredients that will elicit resistance to this stress is needed. Quillaja saponin (QS), a triterpenoid saponin derived from the bark of Quillaja saponaria, is reported to trigger innate immunity in vitro and in vivo in shrimps. The present study aims to evaluate its potential as growth-promoter and its immune-enhancement effects against salinity stress. Three separate experiments were done: (a) an attractability test; (b) a 30-day feeding trial to determine optimal inclusion of QS; and (3) an acute hyposalinity stress test following feeding the experimental diets. Attractability tests showed that all the Quillaja saponin inclusions significantly attracted more shrimps than the control diet (p<0.05). In the feeding trial, 5 experimental diets containing 0.0, 0.15, 0.30, 0.45, and 0.60 g kg-1 QS (QS 0, QS 15, QS 30, QS 45 and QS 60, respectively) were fed to groups of shrimps. Results showed that the final average body weight (FABW), feed intake (FI), weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) values of shrimps in the QS 30 and 45 groups were significantly higher than that of the control group; the values of those in QS 15 and 60 groups were not significantly different from those of the QS 0 group. The optimal inclusion level of dietary QS was estimated to be 0.36 g kg-1. In the acute hyposalinity stress test, shrimps were fed with the experimental diets for 2 weeks and then transferred from 24 PSU salinity media to 2 PSU. All QS groups showed lower cumulative mortality rate than that of the QS 0 group except for the QS 60; QS 30 groups exhibited significantly the lowest. The estimated level of QS that elicited the lowest cumulative mortality rate was 0.33 g kg-1. In conclusion, the diets containing QS enhanced the shrimp's attractability, promoted both growth and immune response against acute hyposalinity stress at the optimal level of 0.36 g kg-1 QS in the black tiger shrimp P. monodon.