Effect of multi-strain probiotics on the growth, hematological profile, blood biochemistry, antioxidant capacity, and physiological responses of Clarias batrachus fingerlings.

This study was designed to evaluate the effects of multi-strain probiotic (MSP) on growth, whole-body composition, digestive and antioxidant enzymes, hematology, blood biochemistry, and physiological stress responses in Clarias batrachus fingerlings. Five experimental diets were prepared with supplementation of MSP (composed of Bacillus subtilis, B. licheniformis, and Enterococcus faecalis) powder at 0.5, 1.0, 1.5, and 2.0 g/kg. Healthy fingerlings (N = 225) were procured from a fish hatchery and acclimatized to laboratory conditions for 15 days. After acclimation, the fingerlings (10.13 ± 0.01 g; mean ± SD) were randomly stocked into five experimental groups (15 fish/aquarium) with three replicates and provided with experimental diets at a 5% body weight ration five times a day for 90 days. Fish fed with 2.0 g/kg MSP diets showed significantly higher growth performance in terms of weight gain % (493.98 ± 6.3%) and specific growth rate (1.97 ± 0.01%/day) and the lowest feed conversion ratio (1.72 ± 0.01) in comparison to the control (299.73 ± 5.17%, 1.53 ± 0.01%/day, and 2.28 ± 0.05, respectively). Similarly, higher activities (p < 0.05) of amylase (1.96 ± 0.02 U/mg protein), protease (10.51 ± 0.06 U/mg protein) and lipase (2.26 ± 0.02 U/mg protein) were also observed in the group fed 2.0 g/kg MSP than in the control group (1.20 ± 0.01, 8.61 ± 0.01, and 1.55 ± 0.02 U/mg protein, respectively). Dietary supplementation significantly (p < 0.05) enhanced the activities of superoxide dismutase (5.86 ± 0.04 U/mg prot), catalase (85.54 ± 0.58 U/mg prot), and glutathione peroxidase (105.69 ± 0.17 μU/mg prot) and reduced the malondialdehyde content (2.13 ± 0.06 mg/g prot) in fish fed 2.0 g/kg MSP-supplemented diets compared to the control group (4.54 ± 0.08 U/mg prot, 70.24 ± 0.53 U/mg prot, 89.61 ± 0.32 μU/mg prot, and 2.77 ± 0.02 mg/g prot, respectively). Dietary MSP did not affect the survival rate and proximate composition of fish. Hematological parameters such as white blood cells, red blood cells, hemoglobin, and hematocrit were also significantly increased in response to MSP supplementation in diets. Moreover, an increasing trend in blood biochemistry was observed in the activities of alanine phosphatase, while a decrease in alanine aminotransferase and aspartate aminotransferase was observed. It is concluded that MSP supplementation up to 2.0 g/kg showed promising results on C. batrachus fingerlings. MSP supplementation significantly enhanced the growth performance, antioxidant and digestive enzyme activities, blood biochemistry, and hematological parameters of C. batrachus compared to the control. The physiological stress response did not show any significant alteration. Thus, MSP can be effectively recommended as an effective growth promotor for fish. [ABSTRACT FROM AUTHOR]