Based on the above data, the increased expression of immunerelated
genes varied in different tissues during the feeding trials,
which may be a “normal” response to a foreign factor and does not indicate
that the probiotics have strengthened the immune system. Therefore
challenge experiments were performed following probiotic
administration, and the results suggest that probiotic- and metaboliteincorporated
diets could enhance the diseases resistance of L. vannamei.
After four weeks of feeding trials, the SGR of shrimp fed with
probiotics was significantly higher than the metabolites and control
groups; surprisingly, the supernatant-feeding shrimp had a lower SGR
than the control group, but this was not significant. This result may indicate
that the supernatant of L. pentosus HC-2 not only has immunestimulating
properties on shrimp but also consumes some energy, and
the interplay of the gut microbiota and host may be important to promoting
the growth of shrimp.