A multitissue transcriptomic analysis reveals a potential mechanism whereby Brevibacillus laterosporus S62-9 promotes broiler growth

Brevibacillus laterosporus S62-9 has been shown to improve broiler growth performance and immunity. In the present study, we aimed to evaluate the effects of B. laterosporus S62-9 on the immunity and lipid metabolism of broilers by means of transcriptomic analysis. A total of 160 1-day-old broilers were randomly allocated to a S62-9 group, the diet of which was supplemented with 106 CFU/g B. laterosporus S62-9 daily, and a control group, which was not. After 42 d of feeding, the broilers in the S62-9 group had higher body mass (7.2%) and feed conversion ratio (5.19%) than the control group. Supplementation with B. laterosporus S62-9 resulted in lower serum total cholesterol and low-density lipoprotein-cholesterol concentrations and higher high-density lipoprotein-cholesterol concentrations. An analysis of the fatty acid composition of the broiler's thigh muscles revealed that the proportions of the unsaturated fatty acids myristoleic acid (C14:1) and arachidonic acid (C20:1) were higher for birds in the S62-9 group. Transcriptomic analysis also showed an upregulation of immunity-related genes in the S62-9 group. Gene Ontology functional enrichment analysis showed that the mitogen-activated protein kinase pathway was enriched in the liver, the defense response was enriched in the duodenum, and immunoglobulin-related entries were enriched in the jejunum of the S62-9 group. Furthermore, the expression of key genes involved in unsaturated fatty acid synthesis (SCD, encoding stearoyl-CoA desaturase) and fatty acid metabolism (HACD2, encoding 3-hydroxyacyl-CoA dehydratase 2) was upregulated in the liver, and the expression of genes associated with fat biosynthesis and accumulation, such as PLIN1, encoding perilipin 1, and FABP4, encoding fatty acid binding protein 4, was upregulated in the ileum of the birds in the S62-9 group. In summary, supplementation with B. laterosporus S62-9 could improve immune defense and the fatty acid metabolism of broiler chickens, thereby enhancing their disease resistance and promoting growth and development.