Effect of adding vegetable substrates on Penaeus vannamei pre-grown in biofloc system on shrimp performance, water quality and biofloc composition

The effect of adding vegetable substrates: wheat bran (WB), oat bran (OB) and amaranth seeds (AS) on water quality, biofloc composition and production response of Penaeus vannamei intensively pre-grown, was evaluated during five weeks. Water quality parameters (temperature, pH, salinity and dissolved oxygen) were monitored twice a day; nitrogenous compounds (TAN, NO2-N, NO3-N) and the total suspended solids (TSS), were recorded weekly. Weight gain and survival of juveniles were monitored each week. Chemical proximate composition of biofloc and content of heterotrophic bacteria were recorded at the end of the trial. No significant differences were observed for any of the water quality parameters or nitrogenous compounds. The TSS was higher in treatments with substrates compared to the control. The treatment WB showed the highest content of heterotrophic bacteria. Organic matter in the bioflocs ranged from 58.3 to 62.4%, proteins from 33.4 to 37.6%, lipids from 0.4 to 0.5% and carbohydrates from 17.1 to 25.5%, without significant differences in any of them among treatments. The mean final weight varied from 1.10 to 1.38 g, and specific growth rate from 5.83 to 6.43% d(-1), with the highest values in treatment OB. Final survival ranged from 93.7 to 98.8% without significant differences among treatments and the control. The feed conversion ratio varied from 0.92 to 1.20 with the lowest value in OB compared to the control. The results suggest that supplementation of substrates does not have a negative effect on water quality, but have positive effects on the productive response of shrimp during their pre-grown, being oat bran the most adequate.