Dietary incorporation of Bacillus subtilis, enhances growth performance, survival rate, gametogenesis and intestinal health, in zebrafish (Danio rerio)

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This study assessed the probiotic effects of dietary supplementation with Bacillus subtilis HBB 493® on growth, survival, gametogenesis, and intestinal health of Zebrafish (Danio rerio). 600 juveniles were divided into five experimental groups namely: Control group I (0.0 cfu/g), group II (6.5x109 cfu/g), group III (1.3x1010 cfu/g), group IV (2.6x1010 cfu/g) and group V(3.9x1010 cfu/g). Each treatment and control had three replicates, while each replicate had 40 fish. The duration of the experiment was 100 days. At the termination of the experiment, gonads, and intestine were histologically assessed. Growth parameters, in the fish fed 3.9x1010 cfu/g were significantly different from those observed in the control, group II, and group III B. subtilis fed groups (P<0.05), and group V was the best. There were no significant differences in the survival rate between treatment groups including control (P>0.05). The histological observations of the gonads reveal differences among the fish fed different levels of B. subtilis. Fish fed diets II, III, IV and V had more developed gonads compared to those on diets without B. subtilis. The status of villus and goblet cells was used to assess the intestinal health of the fish fed diets supplemented with B. subtilis. Villus and goblet cells were intact in all the different levels of B. subtilis supplemented groups. The present study suggested that the dietary supplementation of 3.9x1010 cfu/g probiotic B. subtilis should be used for the enhancement of growth parameters, survival rate, gametogenesis and intestinal health in ornamental zebrafish.