The present study investigated for the first time the gut bacterial responses of Nile tilapia (Oreochromis niloticus) to four different woody forages (Moringa oleifera, fermented M. oleifera, Folium mori and fermented F. mori meals) by high‐throughput Illumina sequencing. Forty‐eight bacterial phyla and a very different bacterial community consisted of Paeniclostridium, Clostridium, Mycobacterium, Synechococcus, Cetobacterium, Trachydiscus and Romboutsia were detected in this study. Interestingly, it was found that the number of bacterial operational taxonomic units (OTUs) in foreguts and hindguts of Nile tilapia in reference diet group was very close, while the number of bacterial OTUs in hindguts was much more than that in foregut of tilapia after fed with different woody forages. These results indicated that woody forages could effectively enhance the diversity and difference of gut bacterial community of tilapia. Furthermore, woody forges might influence the distribution of some unique bacterial community (Desulfovibrio, Thiobacillus, Methylobacillus, Marmoricola and Syntrophobacter) in guts of Nile tilapia, which was confirmed by comparing predicted gut bacterial functions that two pathways including membrane transport and carbon metabolism in four woody forage groups were significantly higher than those in reference diet group. This present study contributed to our understanding of the gut bacterial diversity and functions of Nile tilapia fed with different woody forages.

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