The aim of this study was to investigate the effect of providing supplementary Cr-enriched Bacillus subtilis (CEBS) to mice with regard to their growth performance, caecal microbiology, tissue Cr concentration, insulin receptor (IR) expression and plasma biochemical profile. A total of ninety-six Kunming strain mice were allocated to four different groups: control, CEBS, inorganic Cr and B. subtilis. After 15 d of treatment, mice that received CEBS or normal B. subtilis had higher body weights than control mice, and after 30 d mice given either CEBS or B. subtilis had greater body weights than control mice or those given inorganic Cr. The concentration of Cr in tissues (heart, liver, spleen, kidney and skeletal muscle) increased after CEBS supplementation. B. subtilis and CEBS supplementation caused a significant increase in the numbers of Lactobacillus and Bifidobacterium in the caecum, whereas the numbers of Escherichia coli and Staphylococcus decreased significantly compared with the control. The levels of IR RNA and protein in skeletal muscles increased significantly. Plasma glucose, total cholesterol, TAG and LDL-cholesterol levels declined significantly in the CEBS group compared with the control group, whereas plasma insulin and HDL-cholesterol levels increased significantly. In conclusion, CEBS supplementation enhanced the regulation of body growth, increased tissue organic Cr concentrations, altered caecal microbiota and enhanced IR expression to produce significant changes in plasma biochemistry.
Keywords: ADG average daily gain; CEBS Cr-enriched Bacillus subtilis; Cr-enriched Bacillus; F:G ratio of feed:gain; GAPDH glyceraldehyde phosphate dehydrogenase; Gene expression; Heat stress; IR insulin receptor; Metabolism; Mice; TC total cholesterol.