Lacticaseibacillus casei in Diet of Juvenile Convict Cichlid Fish (Amatitlania nigrofasciata): Evaluating Growth Performance, Digestive Enzyme Activities, Immune Responses, and Stress Resistance.

In this study, growth performance, body composition, digestive enzymes activity, mucosal and immunological parameters, cultivable bacterial populations, and stress resistance were investigated in juvenile convict cichlid fish (Amatitlania nigrofasciata) that received a dietary supplement containing 0 (control), 5 × 106 (LC1), 5 × 107 (LC2), and 5 × 108 CFU g-1 diet (LC3) Lacticaseibacillus casei PB-LC39. Two hundred and forty fish (2.44 ± 0.04 g) were assigned to twelve experimental aquariums and feed ad libitum three times a day for 8 weeks. After final sampling, final body weight, percentage of weight gain (WG %), specific growth rate (SGR), food conversion ratio (FCR), and protein content of whole-body composition were significantly higher (P < 0.05) in fish fed LC1 diet than other treatments. Total protease, amylase, and lipase activities were also significantly higher (P < 0.05) in fish fed LC1 diet than other groups. Total protein from serum and mucus, lysozyme activity, total immunoglobulin (Ig), and serum globulin were significantly increased (P < 0.05) in fish fed LC1 diet compared with other groups. Moreover, total counts of lactic acid bacteria (LAB) in fish gut were significantly higher (P < 0.05) by different levels of L. casei PB-LC39 than the control group. Recovery rates of fish fed the probiotic cells, after an air-dive test, was significantly increased (P < 0.05) compared with the control group. Therefore, the results showed that L. casei PB-LC39 resulted in improving growth, health status, and stress resistance of fish during the rearing of juvenile convict cichlid fish.