Rubber seed cake supplementation alters meat quality, intestinal health, and gut microbiota in Hu sheep

This study aimed to investigate the effects of rubber seed cake (RSC) supplementation on slaughter performance, intestinal health, and gut microbiota in Hu sheep. Forty-eight Hu sheep (17.01 ± 0.57 kg; 3 months old) were randomly allocated to four dietary treatments: 0% (CON), 6% (R6), 12% (R12), and 18% (R18) RSC. Following an 80-day feeding trial, six sheep per group were randomly selected for slaughter. Samples of the longissimus dorsi, small intestine, and intestinal mucosa were collected for meat quality, morphological, and intestinal health analyses. Additionally, ileal contents were harvested and frozen for metagenomic sequencing. Dietary supplementation with RSC reduced the shear force of the longissimus dorsi muscle (P = 0.043) and lowered meat color L* (P = 0.044) and b* (P = 0.035) values in the R6 group compared to the CON group. Quadratic effects were observed for the villus height to crypt depth (VH/CD) ratio in the duodenum (P = 0.006), jejunum (P = 0.006), and ileum (P = 0.001) with increasing RSC supplementation, and the VH/CD ratio was significantly increased in the R6 and R12 groups (P < 0.05). Ileal pro-inflammatory cytokine concentrations, including tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6), decreased both linearly and quadratically with increasing RSC supplementation (P < 0.05). Quadratic effects (P < 0.05) were observed for the concentrations of mucin 2 (MUC2) and tight junction proteins such as zonula occludens-1 (ZO-1), occludin, and claudin in the jejunal and ileal mucosa with increasing RSC supplementation. Specifically, the concentrations of MUC2 and tight junction proteins in the jejunum, as well as MUC2 and ZO-1 in the ileum, were significantly higher in the R6 group (P < 0.05). RSC supplementation significantly altered the relative abundance of specific taxa, including Stenotrophomonas, Piromyces, Lichinomycetes, and Syntrophobacteria, as well as CAZyme gene sequences such as GH119, GT39, and GH13-8 (P < 0.05). In conclusion, these findings indicate that a 6% dietary supplementation of RSC is optimal in Hu sheep, as it improves meat quality and intestinal health by modulating the ileal microbiota composition and CAZyme abundance, thereby strengthening mucosal barrier function and alleviating inflammation.