FUT1 and escherichia coli infection: Interestingly, the expression of AO antigens in the pig’s small intestine is also directly correlate with age, as Prof. Cox’s group has noticed that new-borns are always resistant to F18+ E. coli infection independent of the FUT1 M307 SNP, and that susceptibility to F18+ E. coli infection becomes highest just after weaning at 6–8 weeks old [38].