Effects of organic carbon sources on water quality, microbial flocs protein and performance of Macrobrachium rosenbergii post‐larvae reared in biofloc and synbiotic systems

Abstract

Different strategies for supplying organic carbon in biofloc and synbiotic were tested for Macrobrachium rosenbergii port-larvae (PL). The prawn (0.01 ± 0.002 g) were stocked (0.8 PL L−1) during 35 days in an experimental design with five treatments and four replicates: Ct = control; M = molasses (BFT); Mf = molasses pre-treated with Bacillus spp. without and with aeration (synbiotic); RB = rice bran (BFT); and RBf = raw rice bran pre-treated with Bacillus spp., without and with aeration (synbiotic). The prawns were fed five times a day with a feed containing 40% crude protein. Water quality variables remained within the range considered suitable for the species, and the synbiotic reduced the mean values of settleable solids. The protein content of microbial flocs (dry weight) differed among RBf (34.07 ± 0.54%) and RB (29.77 ± 0.48%), but was higher in M (43.27 ± 0.76%). The prawns submitted to RBf presented the best combination of results for variables final weight (122.85 ± 12.50 mg) and weekly weight gain (22.26 ± 2.97 mg). Thus, RBf treatments (synbiotic) in addition to maintaining water quality variables at acceptable levels can improve growth of M. rosenbergii post-larvae.