To compare the synergistic impact of dietary heat-killed Lactobacillus plantarum and berberine supplementation on intestinal health of juvenile black sea bream, the test fish (5.67 ± 0.05 g) were fed three diets: a basal control diet designated as Con
basal diet supplemented with 400 mg/kg L. plantarum, labelled LP
and basal diet supplemented with 400 mg/kg L. plantarum + 50 mg/k berberine, labelled LPBB. After 56 days of feeding, the control fish had significantly lower intestinal villus height (VH), villus surface area (VSA), and muscularis mucosae (MS) thickness than the rest of the groups (P <
0.05). The LPBB fish had significantly higher VH than the control fish, and wider MS and VSA than the rest of the groups (P <
0.05). Occludin was significantly upregulated in the LPBB fish, and heat shock protein 90 was upregulated in the control fish (P <
0.05). The abundance of Proteobacteria family was significantly higher in the intestinal microbiome of the control and LP fish, the LPBB fish had higher abundance of Cyanobacteria and Spirochaetes, and the LP group had higher Bacteroidetes abundance (P <
0.05). Potentially beneficial Delftia and Brevinema were the significantly abundant genera in the LP and LPBB fish, respectively
potentially pathogenic Elizabethkingia was abundant in the LP fish
and the control fish had higher abundance of potentially pathogenic Burkholderia-Caballeronia-Paraburkholderia (P <
0.05). According to these results, there is possible synergy between L. plantarum and berberine as dietary supplements in fostering healthy intestine for black sea bream than L. plantarum alone.