Abstract：It focuses on the intestinal health that balances in microbial flora. The objective of this study was to examine the variation of gastrointestinal tract microflora in broilers raised under different immune status. Enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) was conducted to evaluate this effect in broilers. Treatments consisted of a negative control, general vaccination, lipopolysaccharide(LPS) + general vaccination and cyclophosphamide(CYP )+ general vaccination. On the age of 21, 28, 35 and 42 d, digesta of duodenum, jejunum, ileum and cecum were collected to assay for gut microflora. The results showed that the DNA fingerprinting of ERIC-PCR had high stability and repetition. The molecular weights of gene fragment were almost from 200 to 2 000 bp after ERIC-PCR amplification. Different immune stress affected gut microflora to different degrees, and as age varied, the dominant microflora correspondingly changed. The diversity of cecal microflora was mostly obvious in LPS+ general vaccination treatment and CYP+ general vaccination treatment. In the present study, based on cluster analysis, the similarity of gut microflora in negative control was relatively stable, and among all treatments, the similarity of duodenal microflora was up to 75%, followed by cecum(40%), jejunum(38%) and ileum(39%). Under different immune status, between LPS group and no vaccination group, the microbial number and distribution in jejunum were different, but there were no significant difference in ileum and cecum between LPS group and CYP group
