Synbiotic of alginate, spirulina water extract, and Lactobacillus bulgaricus promotes survival, growth, and immune parameters based on the gene-expression of Litopenaeus vannamei in low-salinity

Synbiotics containing prebiotics and probiotics are commonly applied in aquaculture, which serves mutual benefits. This study focused on applying alginate, spirulina water extract (SWE), and Lactobacillus bulgaricus probiotics in Litopenaeus vannamei supplementation feed via oral administration at low salinity (1 ppt). The survival rate, growth, and biomass were determined as well as the immune-related gene expression of ProPhenol Oxidase (PO), Superoxide Dismutase (SOD), Lipopolysaccharide Beta Glucan Binding Protein (LGBP) were assessed. Gene-related salinity stressors, namely insulin-like growth Factor (IGF) and Heat Shock Protein (HSP), were also determined. The factorial design with two factors was applied (supplemented and non-supplemented; 1 ppt and 30 ppt mediums) and replicated thrice. 1,000 shrimps (500 ind.m2) at the initial weight of 0.2±0.05 g were reared in the semi-mass culture at 2 tons medium for 56 days. Growth was monitored weekly. The results show that shrimp fed supplementation of (Alg 3.0 g.kg-1 + 5.0 mg SWE.kg-1) in 1 ppt medium (P 0.05) reached the best survival rate, biomass, and gene expression (PO, LGBP, HSP, and IGF), except Lectin. These prebiotics of macro and microalga from Indonesia s tropical coast supported the environmentally friendly and sustainable approach. Promising a noteworthy future in culturing L. vannamei in low salinity.