Bacillus subtilis

3.5 | Probiotic evaluation of dietary B. subtilis View in CoL in darkbarbel catfish

3.5.1 | Growth performance

3.5.2 | Immunological parameters

3.5.3 | Immune-related gene expression

Lipolytic circle diameter (mm) Cellulolytic circle diameter (mm)

17.75 ± 1.94 23.27 ± 1.42

Proteolytic circle diameter (mm) Amylolytic circle diameter (mm)

11.09 ± 1.06 12.46 ± 1.49 supplemented with 0 (T0), 1 10 7 (T1), Initial weight (g)

1 10 8 (T2), and 1 10 9 (T3) CFU/kg of Final weight (g) Bacillus subtilis for 56 days.

Weight gain rate (%)

Special growth rate (%)

Survival rate (%)

T0 T1 T2 T3

42.6 ± 2.9a 43.1 ± 1.6a 41.4 ± 2.1a 41.7 ± 2.4a

62.3 ± 3.5 a 71.2 ± 2.6 b 78.2 ± 2.4 c 79.2 ± 3.2 c 46.47 ± 2.14 a 65.19 ± 6.20 b 89.69 ± 5.14 c 89.92 ± 3.26 c 0.681 ± 0.026 a 0.896 ± 0.067 b 1.143 ± 0.048 c 1.145 ± 0.031 c 98.78 ± 0.09 a 98.61 ± 0.58 a 98.72 ± 0.19 a 98.72 ± 0.25 a

Note: Values with different letters within the same row indicate significant difference ( p <0.05). Weight gain rate (%) (WGR) = [100 (final weight initial weight)/(initial weight)]. Specific growth rate (%) (SGR) = 100 [ln (final mean weight) ln (initial mean weight)]/days.

supplemented with 0 (T0), 1 10 7 (T1), LZM (U/mL)

1 10 8 (T2), and 1 10 9 (T3) CFU/kg of SOD (U/mL) Bacillus subtilis for 56 days.

AKP (U/mL)

T-AOC (U/mL)

MDA (nmol/mL)

T0 T1 T2 T3 47.27 ± 1.82 a 58.65 ± 1.75 b 64.59 ± 1.36 c 69.38 ± 2.14 d 86.15 ± 7.54 a 104.29 ± 5.72 b 118.37 ± 4.68 c 123.98 ± 5.46 d 35.62 ± 3.27 a 43.84 ± 4.18 b 52.93 ± 3.71 c 55.72 ± 5.16 d

8.92 ± 0.25a 11.56 ± 0.49b 15.46 ± 0.68c 18.15 ± 0.37d

2.63 ± 0.05a 2.12 ± 0.07b 1.44 ± 0.06c 1.21 ± 0.05d

Note: Values with different letters within the same row indicate significant difference ( p <0.05). Abbreviations: AKP, alkaline phosphatase; LZM, lysozyme; MDA, malondialdehyde; SOD, superoxide dismutase; T-AOC, total antioxidant capacity.

(transforming growth factor-α [TNF-α], interleukin 1β (IL-1β), IL-10, and transforming growth factor-β [TGF-β]). After 56 days, fish on B. subtilis – supplemented diet exhibited lower relative mRNA expression of TNF-α and IL-1β compared to controls ( p <0.05). In contrast, B. subtilis-fed fish displayed significant increases ( p <0.05) in relative mRNA expression levels of IL-10, TGF-β, IgM, and C3 genes.