Efficacy of in situ and ex situ biofloc on growth, immunephysiological responses, nutrient composition and muscle growth-related gene expression of Etroplus suratensis

A 90-day trial was carried out to investigate the effects of in situ and ex situ biofloc on the immune-physiological responses, nutrient composition and muscle growth-related gene expression.

The experimental groups consisted of IB-1, IB-2, IB-3 (in situ biofloc), EB-1, EB-2, EB-3 (ex situ biofloc). The capacity of 2.4-ton outdoor tanks were stocked with 4.36±0.1 g pearlspot (Etroplus suratensis) juveniles @ 150/m³. Organic jaggery was used as a carbon source to maintain 12:1, 15:1 and 20:1 C/N (IB-1, IB-2, IB-3) ratio for in situ biofloc development and ex situ biofloc mass production and feed supplementation at 10, 20 and 30% graded level in the diet (EB-1, EB-2, EB-3).

At the end of the experiment, in situ biofloc system showed significantly better physiological performances in terms of SOD, RBT, MPO, GLU, CAT and serum protein compared to ex situ treatment. In the ex situ system, biofloc supplemented at 20% significantly improved nutrient composition. There was a significant effect of in situ and ex situ biofloc treatments on whole-body amino acids like phenylalanine, leucine, isoleucine, methionine, tryptophan and lysine. However, the targeted muscle-growth-related myo D gene was significantly upregulated in IB-3 in situ and EB-2 ex situ treatments, while the myostatin was downregulated in IB-3 and EB-2. Therefore, this present study suggests the adoption of the in situ biofloc method to obtain better performance of Pearlspot, in situ biofloc at 20:1 C: N level could be used to improve overall health and muscle growth in Etroplus suratensis.