As immunomodulators, probionts may increase the production
of reactive oxygen metabolites by macrophages. Superoxide anion
along with hydroxyl radicals and nitric oxides are induced reactive
oxygen species, which are associated with enhanced microbial
killing capacity of macrophages [32]. In the present study, dietary
supplementation of L. plantarum VSG3 had no significant effect on
the serum SOD activities after 30 days of feeding; however,
a significant improvement in SOD activity was recorded only in the
fish group fed diet containing 108 cfu g1 L. plantarum VSG3 after 60
days of feeding. Similarly, Sun et al. [20] found that dietary
administration of B. pumilus or Bacillus clausii at 1 108 cfu g1 for
60 days increased the SOD activities in E. coioides. The SOD activities
of L. rohita fed diets containing Pseudomonas aeruginosa at 105, 107,
and 109 cfu g1 had no significant effect on serum SOD activities
after 30 days of feeding; however, the SOD activities increased
significantly after 60 days of feeding [17]. In contrast, dietary
supplementation of L. plantarum for 4 weeks decreased the SOD
activity in E. coioides [13]. Panigrahi et al. [40] reported that dietary
supplementation of L. rhamnosus JCM 1136 in rainbow trout
increased the superoxide anion production upto 20 days of feeding;
thereafter, a decline in SOD activity was observed