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

## TL;DR

Adding Bacillus coagulans to the diet of juvenile fourfinger threadfin fish improves their growth and gut health, though some digestive enzymes decrease.

## Contribution

This study demonstrates the benefits of Bacillus coagulans in aquaculture for enhancing fish growth and intestinal health.

## Key findings

- Fish fed Bacillus coagulans showed better growth and feed conversion compared to the control group.
- Intestinal villi were taller in the experimental group, indicating improved gut structure.
- Digestive enzyme activities like trypsin and amylase decreased, but gut microbiota diversity remained unchanged.

## Abstract

This study examines the effects of adding Bacillus coagulans (a type of beneficial bacteria) to the diet of juvenile fourfinger threadfin fish (Eleutheronema tetradactylum) to improve their growth and gut health. Over an eight-week period, the fish were fed a diet treated with this bacterium, and their growth, digestive enzyme activity, gut structure, and gut bacteria were measured. Results showed that the fish in the experimental group grew better and had a more efficient feed conversion compared to the control group. However, the activities of certain digestive enzymes decreased, and there were no significant changes in the diversity of gut bacteria. The gut structure improved, with the fish having taller intestinal villi. Additionally, certain biological pathways linked to digestion and metabolism were more active in the experimental group. Overall, supplementing the fish’s diet with B. coagulans led to better growth and gut health, which could be valuable for improving fish farming practices and promoting healthier aquatic species.

The effects of Bacillus coagulans (BC) T-21 on growth performance, intestinal digestive enzyme activity, intestinal morphology, and intestinal microbiota of juvenile fourfinger threadfin (Eleutheronema tetradactylum) were investigated in the present study. Healthy juvenile E. tetradactylum with an initial body weight of 4.2 ± 0.5 g were fed a basal diet sprayed with 1 × 108 cfu/g B. coagulans 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 (p < 0.01), whereas the differences in weight gain rate, specific growth rate, survival rate, and condition factor were significant (p < 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 (p > 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 (p < 0.05). However, there were no significant differences in the counts of other functional pathways (p > 0.05). These results indicate that dietary B. coagulans supplementation is effective in promoting the growth performance and intestinal health of juvenile E. tetradactylum.