Effects of culturing the Pacific white shrimp Penaeus vannamei in "biofloc" vs "synbiotic" systems on the growth and immune system

An 8-week indoor experiment was conducted to study the effect of culturing the Pacific white shrimp in "biofloc" and "synbiotic" type system on the growth and immune responses of the shrimp. The experimental system consisted of 24 static indoor circular polypropylene tanks (800 L water volume). Each of the twenty-four tanks were stocked at a density of 125 shrimp/m2 and eight treatments with 3 replicates were assigned using a 4 x 2 factorial design. Four primary treatments included biofloc (T1), synbiotics with beta-xylanase enzyme (T2), synbiotics without enzyme (T3), and a control (T4). These were further assigned to have or not have a small, fluidized bed biofilter. The mean initial weight of the shrimp stocked in the treatments with biofilter was 0.39 +/- 0.02 g, while the mean initial weight in the treatments without biofilter was 0.84 +/- 0.01 g. The growth performance of the whole data set was analyzed by two-way ANCOVA, using the four treatments (T) as the first main factor, the biofilter (B) as the second main factor, and the initial weight as covariable. The results from two-way ANCOVA identified significant differences between treatments in final weights, weight gain, TGC, and FCR with shrimp reared with biofloc management performing the best. In contrast, there was no significant differences in survival (%) of the shrimp cultured between the four treatments. The levels of metabolic enzyme like Alkaline phosphatase (ALP) and Alanine aminotransferase (ALT) were significantly lower in the biofloc and synbiotic with enzyme, indicating better physiological performance in terms of improving of digestive enzymes giving a better growth index. Gamma-Glutamyl Transferase (GGT) was not significantly different. In addition, the cholesterol (CHOL) level of the hemolymph was significantly higher in shrimp produced from the biofloc and synbiotic treatments. A higher level of total haemocyte count (THC) was noted in the shrimp reared in the biofloc and synbiotic treatments as compared with control, however, there was no significant differences between treatments. All treatments produced good survival, rapid growth, low FCR and physiological parameters indicating all are viable options. Consequently, the choice of how to manage the bacterial community should be based on the available resources.