Abstract: The aim of this study was to investigate the effects of walnut green husk and its extract extracted with 25% ethanol on intestinal morphology,mucosal antioxidant activity and microbial diversity of Yellow-feather broilers.144 1-day-old male Yellow-feather broilers were randomly divided into 3 groups with 12 replicates in each group and 4 chickens in each replicate.The control group was fed with basic diet,and the experimental groups Ⅰ and Ⅱ were fed the basic diet with 1% walnut green husk powder or the extract until 70 days old.At the end of the experiment,one chicken was randomly selected and sacrificed from each replicate,small intestine was taken,and villi height and crypt depth of duodenum,jejunum and ileum were measured.The activities of total superoxide dismutase (T-SOD),copper zinc superoxide dismutase (CuZn-SOD),manganese superoxide dismutase (Mn-SOD),total antioxidant capacity (T-AOC),catalase (CAT) and glutathione reductase (GR) in duodenal mucosa were measured.All ileal contents of each chicken were collected and 16S rDNA high-throughput sequencing technology was used to analyze the differences of intestinal microbial diversity and relative abundance.The results showed that,compared with the control group,adding walnut green husk and its extract had no significant effect on villus height,crypt depth and villus height/crypt depth ratio of duodenum,jejunum and ileum (P>0.05).The activities of T-SOD,CuZn-SOD,Mn-SOD,CAT and T-AOC of duodenal mucosa were not significantly affected (P>0.05).After adding walnut green husk and its extract,the number of observed microbial species in ileum increased significantly (P=0.05),the index of microbial diversity and species richness somewhat increased (P>0.05).Firmicutes was the dominant phylum in ileum of broiler in control group,more than 99% of the total bacteria.The addition of walnut green husk and its extract somewhat decreased the relative abundance of Firmicutes,and increased that of Bacteroidetes,but the differences were not significant (P>0.05).Lactobacillus,the dominant genus in the ileum of Yellow-feather broilers in control group,accounting for 71% on average,somewhat decreased by walnut green husk and the extract (P>0.05).Lactobacillus aviarius,Lactobacillus salivarius, Lactobacillus agilis,Lactobacillus ingluviei and Lactoba cillus reuteri were the dominant species in the ileum of Yellow-feather broilers in control group.The abundance of Lactobacillus aviarius was significantly increased after adding walnut green husk and the extract (P<0.05),and the Lactobacillus agilis was significantly increased after adding the extract (P<0.05).It could be concluded that adding 1% walnut green husk or its extract to broiler diet did not affect intestinal morphology and mucosal antioxidant capacity,but intestinal microbial diversity and species richness increased,and the abundance of beneficial bacteria such as Lactobacillus aviarius and Lactobacillus agilis increased.

Key words: walnut green husk; Yellow-feather broiler; intestinal morphology; microbial diversity; high-throughput sequencing of 16S rDNA