TLRs are an ancient conserved family of pattern-recognition receptors that play a critical role in recognising microbial pathogens and modulating antimicrobial host defence.56 TLR4 is the best-characterised member of this family and is activated by endotoxin or lipopolysaccharide (LPS) from Gram-negative bacteria and initiates the systemic inflammatory response syndrome.57,58 Here, we discovered that duodenal TLR4 mRNA level and its down-stream signals, including MyD88, IRAK1 and TRAF6, were decreased in AOS-treated pigs. The gene discussed is IRAK1; the disease is systemic inflammatory response syndrome.