Effects of Taraxacum and Astragalus extracts combined with probiotic Bacillus subtilis and Lactobacillus on Escherichia coli-infected broiler chickens.

Diarrhea caused by Escherichia coli (E. coli) is one of the most common diseases that affects the growth and development of poultry. This study was conducted to investigate the synergistic effects of traditional Chinese medicine (TCM) combined with probiotics against E. coli infection and its mechanism in broiler chickens. The optimal proportion formula TCM and probiotics was screened by orthogonal test and range analysis method; the in vitro antibacterial activity was based on the Oxford cup method. Isolated pathogenic E. coli was injected subcutaneously into the neck of the broilers to establish an E. coli-infected model. The broilers were administrated with drugs in drinking water daily for 7 d before and after E. coli infection. The diarrhea rate, mortality, body weight (BW) gain, feed intake, immune organ index, intestinal and hepatic histopathological changes were monitored. The expression of IL-2, IL-10, and TLR-4 mRNA in the intestinal tissues was measured by RT-PCR. Our results showed that the optimal proportion formula of Taraxacum extracts: total flavonoids of Astragalus: polysaccharides of Astragalus: probiotics was 5: 2: 2: 2; TCM combined with probiotics was highly sensitive to E. coli. TCM combined with probiotics synergistically increased BW gain, decreased the diarrhea rate and mortality of broilers, alleviated intestinal and hepatic pathological changes, accompanied by the increase of IL-2 and IL-10 mRNA expression and the inhibition of TLR-4 mRNA expression. It suggests that the combination of TCM and probiotics may produce a synergistic protective effect against E. coli infection by improving the indicators of diarrhea and regulating the expression of IL-2, IL-10, and TLR-4 mRNA in broiler chickens. The synergistic interactions between TCM and probiotics represent a promising strategy for the treatment of E. coli infection.