In this study, the influence of commercial probiotic, Lactobacillus spp., supplementation was investigated on
growth parameters and digestive enzyme activities in gilthead sea bream, Sparus aurata, during larval
development. All experiments were triplicated and designed in three different administrations of probiotic
from 3 days after hatching (DAH) concurrently with starting of exogenous feeding. In the first group,
probiotic was added to live food (rotifer and Artemia). In the second group, probiotic was supplemented
directly to both live food and water. In the third group, probiotic was added directly to water. Also, no
probiotic treatment was maintained in control group. Total bacterial counts among probiotic probioticsupplemented
groups were significantly different from total bacterial counts in controls in water and
digestive tract of larvae (pb0.05). The mean of total bacterial counts in control was approximately 4×104-fold
increased from the experimental groups in the sea water (pb0.05). Besides, mean digestive enzyme activities
of all probiotics treatment groups were significantly different (pb0.05) with that of the control. Except
probiotic water supplementation group, in all treatments, the specific activities of pancreatic and intestinal
enzymes were significantly higher (pb0.05) in larvae to which probiotic had been supplemented by live food
and live food with water. Also, S. aurata larvae that had probiotic administered by live food with water
demonstrated significant (pb0.05) increases in both survival (13–105% higher) and specific growth rate (2–
9% higher) as compared to controls. As a result, supplementation of probiotic to directly tank water could not
significantly increase growth parameters and digestive enzyme activities and therefore, administration of
probiotics by this method would not be effective in terms of husbandry parameters and nutritional condition.