Effects of <i>Bacillus coagulans</i> on Growth Performance, Digestive Enzyme Activity, and Intestinal Microbiota of the Juvenile Fourfinger Threadfin (<i>Eleutheronema tetradactylum</i>)

The effects of <i>Bacillus coagulans</i> (BC) T-21 on growth performance, intestinal digestive enzyme activity, intestinal morphology, and intestinal microbiota of juvenile fourfinger threadfin (<i>Eleutheronema tetradactylum</i>) were investigated in the present study. Healthy juvenile <i>E. tetradactylum</i> with an initial body weight of 4.2 ± 0.5 g were fed a basal diet sprayed with 1 × 10⁸ cfu/g <i>B. coagulans</i> for eight weeks, and the growth parameters, intestinal digestive enzyme activities, HE-stained intestinal sections, and intestinal microbiota of the juvenile fish were measured. The differences in the feed conversion ratio between the experimental and control groups (fed the basal diet) were extremely significant (<i>p</i> < 0.01), whereas the differences in weight gain rate, specific growth rate, survival rate, and condition factor were significant (<i>p</i> < 0.05). In the experimental group, trypsin and amylase activities decreased significantly, whereas there were no significant differences in lipase activity between the two groups. Compared to the control group, the height of the intestinal villi was greater. No significant differences were observed in the diversity of intestinal microbiota and microbial species at the genus level (<i>p</i> > 0.05). Based on the function prediction analysis, the count values for the glycan biosynthesis, metabolism, and digestive system pathways were significantly increased in the experimental group (<i>p</i> < 0.05). However, there were no significant differences in the counts of other functional pathways (<i>p</i> > 0.05). These results indicate that dietary <i>B. coagulans</i> supplementation is effective in promoting the growth performance and intestinal health of juvenile <i>E. tetradactylum</i>.