Comparative evaluation of dietary probiotics <i>Bacillus subtilis</i> WB60 and <i>Lactobacillus plantarum</i> KCTC3928 on the growth performance, immunological parameters, gut morphology and disease resistance in Japanese eel, <i>Anguilla japonica</i>

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>The current experiment was conducted to evaluate and compare the efficacy of two different probiotics <I>Bacillus subtilis</I> WB60 and <I>Lactobacillus plantarum</I> KCTC3928 in diet of Japanese eel, <I>Anguilla japonica</I>. Seven experimental diets were formulated to contain no probiotics (CON), three graded levels of <I>B. subtilis</I> at 10<SUP>6</SUP> (BS<SUB>1</SUB>), 10<SUP>7</SUP> (BS<SUB>2</SUB>), 10<SUP>8</SUP> (BS<SUB>3</SUB>) and <I>L. plantarum</I> at 10<SUP>6</SUP> (LP<SUB>1</SUB>), 10<SUP>7</SUP> (LP<SUB>2</SUB>), 10<SUP>8</SUP> (LP<SUB>3</SUB>) CFU/g diet. Twenty fish averaging 8.29 ± 0.06 g were distributed in to 21 aquaria and were randomly assigned to one of the experimental diets in triplicate groups. Average weight gain (WG), feed efficiency (FE), and protein efficiency ratio (PER) of fish fed <I>B. subtilis</I> at 10<SUP>7</SUP> (BS<SUB>2</SUB>) and 10<SUP>8</SUP> (BS<SUB>3</SUB>) CFU/g diet were significantly higher than those of fish fed other experimental diets (<I>P</I> < 0.05). Nonspecific enzymatic activities including lysozyme, superoxide dismutase (SOD), myeloperoxidase (MPO) from fish fed <I>B. subtilis</I> at 10<SUP>7</SUP> (BS<SUB>2</SUB>) and 10<SUP>8</SUP> (BS<SUB>3</SUB>) CFU/g diet were detected to be significantly higher than that from fish fed CON diet (<I>P</I> < 0.05). Whereas, level of intestine glyceraldehyde-3-phosphate dehydrogenase (GAPDH), heat shock protein 70, 90 (HSP70, 90) and immunoglobulin (IgM) from fish fed <I>B. subtilis</I> at 10<SUP>7</SUP> and 10<SUP>8</SUP> CFU/g diet were recorded to be significantly higher than those of fish fed other experimental diets (<I>P</I> < 0.05). Parameters for intestinal morphology and histology suggested a healthier gut for the fish fed10<SUP>8</SUP> (BS<SUB>3</SUB>) CFU/g diet as compared to other treatment groups. Whereas, results from the disease challenge test with bacteria <I>Vibrio angulillarum</I> showed significantly lower survival rate for fish fed CON diet than those of fish fed other experimental diets. Therefore, these results indicated that oral supplement of <I>B. subtilis</I> at 10<SUP>8</SUP> (BS<SUB>3</SUB>) CFU/g diet could be a more effective source of probiotic compared to <I>L. plantarum</I> in Japanese eel.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Preliminary report comparing two probiotics, <I>Bacillus subtilis</I> WB60 and <I>Lactobacillus plantarum</I> KCTC3928. </LI> <LI> Differences on the growth performance, survival rate, immune parameters and gut morphology were clearly observed. </LI> <LI> Oral administration of bacteria spp. <I>B. subtilis</I> at 10<SUP>7</SUP> CFU/g kg<SUP>−</SUP> <SUP>1</SUP> diet could be a more promising source and dose compared to probiotic <I>L. plantarum</I> in freshwater aquaculture. </LI> </UL> </P>