Assessment of Performance, Microbial Community, Bacterial Food Quality, and Gene Expression of Whiteleg Shrimp (Litopenaeus vannamei) Reared under Different Density Biofloc Systems

Abstract

Biofloc shrimp culture, as a way of improving shrimp production, gains worldwide consideration. However, the effects of the biofloc system on shrimp culture at high densities could be a challenge. Here, this study is aimed at identifying a better stocking density of whiteleg shrimp (Litopenaeus vannamei) between two intensive biofloc systems of 100 and 300 org./m2. Achieving that was done by comparing growth performance, water quality, feed utilization, microbial loads from water and shrimps, and gene expression of growth, stress, and immune-related genes. Shrimp postlarvae with a mean weight of 35.4 ± 3.7 mg were reared in six indoor cement tanks (36 m3 total capacity each) at two stocking densities (3 replicates each) for a rearing period of 135 days. Better final weight, weight gain, average daily weight gain, specific growth rate, biomass increase percentage, and survival rate were associated with lower density (100/m2), whereas high-density showed significantly higher total biomass. Better feed utilization was found in the lower density treatment. Lower density treatment enhanced water quality parameters, including higher dissolved oxygen and lower nitrogenous wastes. Heterotrophic bacterial count in water samples was recorded as 5.28 ± 0.15 and 5.11 ± 0.28 log CFU/ml from the high- and low-density systems, respectively, with no significant difference. Beneficial bacteria such as Bacillus spp. were identified in water samples from both systems, still, the Vibrio-like count was developed in the higher density system. Regarding shrimp food bacterial quality, the total bacterial count in the shrimp was recorded as 5.09 ± 0.1 log CFU/g in the 300 org./m2 treatment compared to 4.75 ± 0.24 log CFU/g in the lower density. Escherichia coli was isolated from the shrimps in a lower density group while Aeromonas hydrophila and Citrobacter freundii were associated with shrimps from a higher density system. Immune-related genes including prophenoloxidase, superoxide dismutase (SOD), and lysozyme (LYZ) expressions were all significantly higher expressed in the shrimp from the lower density treatment. Toll receptor (LvToll), penaiedin4 (PEN4), and stress-related gene (HSP 70) showed a decreased gene expression in the shrimp raised in the lower density. Significant upregulation of growth-related gene (Ras-related protein-RAP) expression was associated with the lower stocking density system. In conclusion, the current study found that applying high stocking density (300 org./m2) contributes negatively to performance, water quality, microbial community, bacterial food quality, and gene expression of immune, stress, and growth-related genes when compared with the lower stocking density system (100 org./m2) under biofloc system.

Evaluation of feeding table optimizations in Pacific white shrimp nursery biofloc systems

“…This inoculum consisted of a diverse microbial community composed of nitrifying and heterotrophic bacteria, developing in suspension in the water (Martins et al, 2022). This microbial community is essential for the establishment of a stable and functional ecosystem, because it promotes the transformation of organic waste into solid particles, which serve as a natural food source for shrimp in the nursery stage (Said et al, 2022).…”

Influence of stocking density on the growth, immune and physiological responses, and cultivation environment of white-leg shrimp (Litopenaeus vannamei) in biofloc systems

“…The aeration line, consisting of 2-inch pipes, was divided into units with flow regulators to fine-tune air compression in all ponds. A network of disk diffusers (each measuring 26 cm) was securely fixed and installed at the bottom of each pond to ensure effective aeration and thorough mixing of the culture water across all ponds 4 .…”

“…vannamei ) with a mean body weight of 0.02 ± 0.001 g were stocked at densities of 50 and 200 organisms/m 2 , with triplicates for each treatment. To establish the BF, we followed the method outlined by Said et al 4 . Wheat flour, containing 58.3% carbon, was introduced once daily to all experiments as a carbohydrate source to stimulate the development of the BF community 26 .…”

“…Systems that do not exchange water limit the selection of cultured species to those that can tolerate multiple stressors, such as turbid water, intermediate dissolved oxygen, and suspended solids 3 , 4 . Microbial flocs are beneficial for shrimp rearing, as shrimp can graze on them, converting them into animal protein.…”

The P4’ Peptide-Carrying Bacillus subtilis in Cottonseed Meal Improves the Chinese Mitten Crab Eriocheir sinensis Innate Immunity, Redox Defense, and Growth Performance

“…Over the last few decades, aquaculture has become the fastest growing sector of animal food for human consumption. As the world's population continues to grow, a large-scale and intensive culture mode is not only necessary to upgrade the aquaculture industry, but also to feed the increasing population [ 1 , 2 ]. This culture mode guarantees a high production of aquatic products in a limited space, as boosts the economic efficiency.…”