Journal
FISH & SHELLFISH IMMUNOLOGY
Volume 46, Issue 2, Pages 225-231Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.fsi.2015.06.018
Keywords
Bacillus licheniformis; Growth; Immunity; Intestinal morphology; Streptococcus iniae; Oreochromis niloticus
Funding
- Project of Marine Fishery Science and Technology Extension of Guangdong Province [A201301C02]
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The effects of oral administration of Bacillus licheniformis on growth performance, immunity, intestinal morphology and disease resistance of juvenile tilapia were investigated. Six experimental diets supplemented with different concentrations of B. licheniformis (0%, 0.02%, 0.04%, 0.06%, 0.08% and 0.1% of AlCare (R), containing live germ 2 x 10(10) CFU/g) were formulated, viz. control, T-1,T-2, T-3, T-4 and T-5. Each diet was randomly assigned to triplicate groups of 30 fishes (3.83 +/- 0.03 g). After 10 weeks of feeding trial, weight gain (WG), final body wet weight (FBW) and specific growth rate (SGR) increased significantly in groups T-2, T-3, T-4 and T-5 compared with control and T-1 (p < 0.05). However, survival rate and feed conversion ratio (FCR) were not found to be significantly affected (P > 0.05). Compared with control, dietary B. licheniformis supplementation increased the content of complement C3 in serum significantly (P < 0.05). The lysozyme activity was observed to be highest in T2 (P < 0.05) without differences among other groups. However, SOD activity was not affected by B. licheniformis supplementation (P > 0.05). When tilapia were challenged against Streptococcus iniae, survival rate improved significantly when tilapia fed with T2, T3, T4 and T5 (P < 0.05). Although there was no significant differences in villi length and muscular layer thickness of anterior intestinal among the treatments, intestinal villi of fish fed with higher concentrations of B. licheniformis (T-2, T-3, T-4, T-5) tended to be regularly arranged and exhibited less exfoliation, twist and fusion. These results indicated that dietary supplementation of B. licheniformis not only increased the growth, immune response and disease resistance of juvenile tilapia, but also influenced anterior intestinal development and integrity. Furthermore, in our study, the optimal concentration of B. licheniformis in diets for tilapia was greater than or equal to 4.4 x 10(6) CFU/g. (C) 2015 Elsevier Ltd. All rights reserved.
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