The protection afforded the postlarvae by Streptomyces treatment
groups (T1, T2 and T3) were not significantly different than from the
commercial probiotic (T5). The commercial probiotic used in this
experiment was labelled as a mixture of Bacillus subtilis, B.
licheniformis and B. pumilus. The efficiency of the Streptomyces could
be improved by optimising the dose and the mode of application. The
study was conducted in the small jugs where water was exchanged
daily, which might not allow Streptomyces to colonise completely
(even though Streptomyces were recovered from the animals and their
faeces). Microorganisms only produce metabolites during the stationary
growth phase and if complete colonisation does not occur in
the gut due to constant flushing, total protection may not be observed.
In addition, as suggested by Vine et al. (2004) for other bacterial
probiotics, the growth of Streptomyces may be less than the rate of