Abstract: The study was aimed to investigate the effects of high fiber diet on growth performance, meat quality and intestinal health of growing-finishing pigs. A total of 72 healthy cross-bred (Duroc×Landrace×Large White) pigs with an average body weight of (48.83±0.49) kg were randomly divided into control group and high-fiber group with four replicates in each group and nine pigs per replicate. The trial lasted for 84 days. Pigs in the control group were fed with basal diet, pigs in the high fiber group were fed with the high fiber diet with 15% wheat bran, and the late stage (six weeks later) the two groups were both fed with the high fiber diet. The initial body weight, body weight every three weeks, final weight and feed consumption of each pig were determined. At the end of the experiment, the longissimus dorsi was taken to detect meat quality and muscle fiber characteristics, ileum sample was taken to detect intestinal morphology and intestinal barrier related indexes, cecum and colon contents were taken to detect intestinal microbiome and their metabolites. The results showed that compared with the control group, at 1-3 weeks of the experiment,the body weight(BW) at the third week and average daily gain (ADG) in high fiber group were significantly decreased (P<0.05) and the ratio of feed intake to gain (F/G) was significantly increased (P<0.05). At 7-9 weeks of the experiment, the weight of the high fiber group at the 9th week was significantly higher than that of the control group (P<0.05), and ADG had an increasing trend (P=0.055). During the whole experiment, ADG in the high fiber group increased significantly compared with the control group (P<0.05). In the high fiber group, the 24 hours after slaughter pH (pH24_h) of meat samples increased significantly (P<0.05), the cross-sectional area of muscle fibers was significantly decreased (P<0.05) and the mRNA expression level of MyHC I, which determines the type of muscle fiber was significantly increased(P<0.05) compared with the control group. Compared with the control group, villus height and villus height to crypt depth ratio (V/C) of ileum were extremely significantly increased in the high fiber group (P<0.01),the crypt depth was significantly decreased (P<0.05), while the mRNA expression levels of tight junction protein Claudin-1 and Occludin were significantly increased (P<0.05). Compared with the control group, the number of goblet cells in the high fiber group was extremely significantly increased (P<0.01), and the mRNA expression level of Muc-2 was significantly increased (P<0.05). Compared with the control group, the relative abundance of Firmicutes and Proteobacteria in cecum of the high fiber group were extremely significantly increased (P<0.05), whereas the relative abundance of Bacteroidetes was extremely significantly decreased (P<0.01), the relative abundance of Clostridium was significantly increased (P<0.05), while that of Streptococcus was significantly decreased (P<0.05). In the colon, the relative abundance of Bacillus was extremely significantly increased (P<0.01), while that of Spirochaetes and Streptococcus was extremely significantly decreased (P<0.01) in the high-fiber group. In the cecum, compared with the control group, the concentrations of acetic acid (P<0.05), propionic acid (P<0.05) and butyric acid (P<0.05) were significantly increased in high fiber group. In the colon, the concentrations of acetic acid (P<0.05), propionic acid (P<0.05), butyric acid (P<0.05), valerate acid (P<0.05) and isovalerate acid (P<0.05) were significantly increased. In conclusion, adding 15% wheat bran to the diet of growing-finishing pigs can improve the growth performance, significantly increase the longissimus dorsi pH_{24 h} of finishing pigs, reduce the cross-sectional area of muscle fiber, promote the expression of slow muscle fiber related genes, improve intestinal morphology, intestinal barrier and intestinal microbial composition, increase the production of short chain fatty acids, which is beneficial to the body health and reduction of feeding cost.

Key words: fiber, growing and finishing pigs, growth performance, meat quality, intestinal microbiome