In Hubbard chickens, the NE + XT group had increased percentages of Lactobacillus and Streptococcus, and decreased fractions of Selenihalanaerobacter and Variovorax compared with the NE group. In Ross chickens, the NE + XT group had increased percentages of Selenihalanaerobacter, Clostridium,Calothrix, and Geitlerinema and decreased fractions of Lactobacillus,Streptococcus, and Variovorax compared with the NE group.