Comparison of mucin gene expression between the four animal groups on PND1 and PND6. Transcription of Muc1, Muc2, Muc3, Muc4 and Tff3 on postnatal days (PND) 1 and 6 for pups in groups: GF, SPF, Lb and Ec. Each column represents the average relative abundance (Ra) (See Methods) of 8 animals. Error bars show SEM values. * p < 0.05, ** p < 0.01, *** p < 0.001 relative to PND1 (for the same group) + p < 0.05, ++ p < 0.01, +++ p < 0.001 relative to GF (for the same day).