Prebiotics, probiotics and synbiotics are widely recognized as functional feed additives in aquaculture. Probiotics can enhance intestinal health and immunity by modulating gut microbiota, while prebiotics selectively promote the growth of beneficial bacteria. Synbiotics, a combination of both, may provide synergistic effects on growth performance and disease resistance. However, limited information is available regarding their dietary application for parrot fish. This study was conducted to evaluate the effects of dietary supplementation with prebiotic, probiotics and synbiotic on the growth performance and health status of parrot fish.
A basal diet (Con) containing 45% fish meal (anchovy) and 15% soybean meal was composed of 42.2% protein and 15.9% lipid. Five experimental diets were formulated to include 0.4% mannan oligosaccharide (MOS), 0.4% Lactobacillus plantarum (LP), 0.4% Bacillus subtilis (BS), 0.4% B. licheniformis (BL) and 0.1% MOS + 0.1% LP + 0.1% BS + 0.1% BL (SYN). Total 360 fish (116 ± 1.01 g) were randomly distributed into 18 tanks (300 L) in three replicates and fed the diets for 49 days.
Final body weight was significantly higher in LP, BS, BL and SYN groups than in Con group. Weight gain and specific growth rate were significantly higher in all experimental groups than in Con group. Survival was significantly higher in BL and SYN groups than in Con group. Protein efficiency ratio was significantly higher in BL group than in Con group. Feed conversion ratio was significantly lower in BL group than in Con group. Trypsin and lipase activities in intestine were significantly increased in LP, BS, BL and SYN groups than in Con and MOS groups. Chymotrypsin activity was significantly increased in MOS, LP and BL groups than in Con group. Lysozyme and myeloperoxidase activities were significantly higher in LP group than in Con group. Immunoglobulin level was significantly higher in LP, BS and BL groups than in Con group. Superoxide dismutase activity was significantly higher in MOS, LP, BL and SYN groups than in Con group. Catalase activity was significantly higher in LP, BS, BL and SYN groups than in Con and MOS groups. Disease resistance against Edwardsiella tarda was significantly improved in BS and SYN groups than in Con group.
This study suggests that dietary supplementation of MOS, LP, BS, BL and SYN can improve the growth, feed utilization efficiency, survival, innate immunity, digestive enzyme activity, antioxidant capacity and disease resistance against E. tarda in parrot fish.