Introduction
Biofloc system uses the presence of microorganisms in the fish culture system to generate flocs from nitrogen waste, thus permitting continued water usage. Factors like carbon source, carbon to nitrogen ratio, and stocking density, affect the quality and density of microorganism and the productivity of the biofloc system (Martínez-Córdova et al., 2007). This study aims to determine the growth, feed conversion ratio (FCR), and proximate composition of catfish reared in a biofloc system using rice bran (RBB), fermented rice bran (FRB), and hydrolyzed rice bran (HRB) as carbon sources.
Methods
Fingerling catfish of an initial mean weight of 10.55 ± 2.60g were stocked in outdoor 200-liter plastic tanks in a randomized design with the three treatments in two replications. A biomass (g) to volume (l) ratio of 1:2 was maintained throughout the experiment. The carbon-nitrogen contents in the feed and water were used to ensure an overall 15:1 C-N content in the system. Water parameters were monitored and the growth in length and weight of catfish in biofloc system was recorded weekly for 8 weeks. The proximate composition of the fish reared in biofloc was also determined using standard method of AOAC, (1999). The data obtained were subjected to one way ANOVA to test for significant difference in the survival, weight gained, specific growth rate, and proximate composition among the treatment.
Results
The weight parameters at the end of the 8-week rearing trials showed the catfish culture using RBB (81.15 ± 3.1g), FRB (88.50 ± 5.7 g), and HRB (97.20 ± 2.5 g) were significantly different (P˂0.05) (Table 1). A similar trend was observed in the feed conversion ratio. The crude protein (65.44%) and protein retention (47.2%) were significantly higher (P˂0.05) in the FRB and lowest in the RBB, with values of (61.85%) and (58.5%), respectively. This results showed that acid-hydrolysis and solid-phase fermentation of rice bran could boost its performance as a biofloc carbon source.