Effects of Bacillus halophilus on growth, intestinal flora and metabolism of Larimichthys crocea

Abstract

The incorporation of probiotics into the diet of large yellow croaker has been demonstrated by several studies to confer partial disease resistance. Bacillus halophilic isolated from the intestinal flora was used to study its effects on performance growth indicators, intestinal tissue structure, intestinal flora and the metabolism of Larimichthys crocea. A total of 180 fishes with an initial body weight of (164.00 ± 54.00) g were fed diets with three different concentrations of Bacillus halophilic: 0 cfu/mL (FC0, control group), 108 cfu/mL (FC8, treatment group), and 1012 cfu/mL (FC12, treatment group). The results showed that there were no significant differences in specific growth rate among all groups (P > 0.05). Compared to the FC0 group, the final body weight and Weight gain rate were significantly higher in FC8 and FC12 groups (P 0.05). At the level of intestinal structure, there were no significant differences in villus height, crypt depth and goblet cell number between control group and treatment groups (P > 0.05). At the phylum level, Firmicutes was the dominant phylum, and the genus level, Lactobacillus and Bacteroides were the dominant bacteria in FC8 and FC12. A total of 1070 metabolites were identified, among which lipid metabolites accounted for 46.7%. Metabolites were involved in six main ways, mainly related to the metabolism of amino acids and lipids. The correlation analysis between microbes and metabolites showed that the intestinal flora of Larimichthys crocea could promote the synthesis of metabolites, among which Bacteroides and Megamonas could promote the synthesis of beneficial metabolites such as amino acids and vitamins. Through this study, we found that Bacillus halophilic can significantly improve growth, the antioxidant immunity ability and promote the expression of growth related metabolites, with the FC12 group being the better successful.

Keywords

• Bacillus halophilic
• Larimichthys crocea
• Growth
• Antioxidant immunity
• Intestinal structure
• Intestinal flora