COMPARATIVE EFFECTS OF MOLASSES, SUGAR AND RICE BRAN AS CARBON SOURCES ON WATER QUALITY, GROWTH, AND IMMUNITY OF GIFT TILAPIA IN BIOFLOC SYSTEM

Abstract

Biofloc technology (BFT) is a highly potential biofloating method to aquaculture that promotes nitrogen efficient usage, produces microbial biomass, and could improve fish growth and health. The choice of an appropriate carbon source, however, is crucial for optimizing water quality and production performance. The molasses, sugar and rice bran were compared for use as carbon sources in the culture of genetically improved farmed tilapia (GIFT) in biofloc culture. Four experimental treatments were tested, which comprised of the control without supplemental carbon, molasses, sugar and rice bran. The water quality, growth performance, feed conversion, hematological parameters, innate immune responses and antioxidant indicators were assessed. The results showed that for total ammonia nitrogen and nitrite-nitrogen, molasses supplementation resulted in the lowest levels and highest level was for rice bran, respectively, while for total suspended solids and settleable floc volume, the highest level was found in molasses and the lowest in rice bran, respectively. The fish that were fed molasses had the highest final body weight, weight gain, survival and biomass with the lowest FCR. The growth and physiological responses obtained after sugar supplementation were generally intermediate and moderate in rice bran although high floc development was observed. The comparative pattern of the hematological parameters (hemoglobin concentration, hematocrit), immune parameters (lysozyme activity, phagocytic activity and respiratory burst) was similar. The highest activities of antioxidant enzymes were observed in molasses treatment along with minimum malondialdehyde value. Based on the results of this study, it is hypothesized that carbon source treatment used in GIFT biofloc systems can affect the microbial community, nitrogen removal, growth efficiency and physiological status of the fish. Molasses seems to be a good candidate for further trials, however, the suitability is dependent on the cost, availability and the conditions of the system management.