EFFECT OF DIETARY PREBIOTICS ON BIOFLOC BACTERIAL PROFILE AND PACIFIC WHITE SHRIMP Litopenaeus vannamei PRODUCTION AND HEALTH

Misael Rosales*, Jonathan P. Holt, Michael E. Hume, Charles Hernandez, Delbert M. Gatlin III, and Addison L. Lawrence.  
Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX 77843 USA / trū Shrimp Company, Ralco® Nutrition Inc., Balaton, MN 56115 USA.  
misaelrosales@tamu.edu
 

Prebiotics are generally regarded as safe compounds that confer beneficial effects on intestinal bacteria of cultured animals when provided as dietary additives. However, the effect of prebiotics on bacteria of biofloc particles (BFP), as well as their effect on production and health of Pacific white shrimp Litopenaeus vannamei cultured in a biofloc technology system (BFT), a system that relies highly on bacteria composition, needs to be further examined.

A 31-day feeding trial was performed to evaluate the effects of dietary inclusion of the prebiotics fructooligosaccharide (FOS), galactooligosaccharide (GOS), inulin (INU) and mannan-oligosaccharide (MOS) and the non-prebiotic water-soluble disaccharide sucrose (SUC) on the bacterial profile of BFP and L. vannamei production and health, as indicated by the total hemocyte count (THC). Shrimp weighing 2.0 ± 0.5 g were stocked into each tank (0.457 m x 0.457 m x 0.280 m) at a density of 344 shrimp/m3. Tanks containing an independent heater, an automatic 48-h feeder, and two air stones were filled to 20-cm depth with 28 ppt seawater at 30.0 ± 1.0ᵒC. Each tank was maintained as an individual BFT with two phases. During first phase (day 0-7) and during the second phase (day 8-31), autotrophic and heterotrophic bacteria dominance were promoted, respectively. Only during the second phase, shrimp were fed with 23% protein content experimental diets containing a 3% inclusion level of either FOS, GOS, INU, MOS or SUC. A 23% protein content control diet (CTL) with no additive inclusion was also used only during the second phase. Each diet was provided to each tank according to its treatment in replicates of 4 tanks per treatment.

The bacterial profile comparison, based on denaturing gradient gel electrophoresis, of the dietary treatments and a BFP sample collected on day 6 (autotrophic bacteria dominance; ATr), showed that the ATr and CTL were different from each other, they were different from the prebiotics and SUC treatments, and the SUC and prebiotics treatments were similar (Figure 1). Mean weight gain, survival, feed conversion ratio (FCR) and biofloc level showed no significant (p ≤ 0.05) differences among treatments (Table 1). A significant (p ≤ 0.05) increase was observed in the THC of shrimp fed diets containing MOS (Table 1).

In conclusion, the dietary prebiotics and SUC changed the bacterial communities present in BFP. The bacterial communities of the prebiotic and SUC treatments were similar probably because these additives were similarly available to the bacteria. The higher THC of shrimp fed the MOS treatment is a promising result that needs to be evaluated in shrimp subjected to stress conditions.