Background: Juvenile
Yoshitomi tilapia is often infected by pathogens and results in low-level survival rate.
Bacillus subtilis, as a probiotic, may have beneficial effects on
Y. tilapia with compound 1-deoxynojirimycin (DNJ), which
has antibacterial activities. The effects of dietary probiotic supplementation on
Y. tilapias were evaluated.
Results: Juvenile
Y. tilapia was fed with
B. subtilis for 56 d.
Y. tilapia was infected by
Aeromonas hydrophila
and
survival rate was compared. Dietary
B. subtilis increased weight gain rate, specific growth, food conversion ratios
and food intake rate of
Y. tilapia. The diet improved the cumulative survival rate (CSR) of juvenile
Y. tilapia when
the concentration of
B. subtilis was more than 2.05 × 10
10 cfu/kg and CSR reached a maximum rate when the
concentration of bacillus was 4.23 × 10
10 (
P < 0.05). Meanwhile,
B. subtilis improved total antioxidant capacity
(TAC), spleen index, the activities of serum lysozyme, alkaline phosphatase (ALP), superoxide dismutase (SOD)
and catalase (CAT) (P b 0.05). In contrast,
B. subtilis reduced serum aspartate aminotransferase (AST), alanine
aminotransferase (ALT), malondialdehyde (MDA) and C3 complement (
P < 0.05). DNJ was isolated from
secondary metabolisms and proved to increase the levels of SOD, CAT and reduce the levels of AST, ALT and MDA
at cell levels. After
A. hydrophila infection, DNJ prevented the reduction in survival rate of
Y. tilapia (
P < 0.05).
Conclusions: 1-Deoxynojirimycin from
Bacillus subtilis can be used to improve the growth performance of
juvenile
Y. tilapia by affecting its antioxidant and antibacterial activities.
