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Acta Prataculturae Sinica ›› 2024, Vol. 33 ›› Issue (12): 188-200.DOI: 10.11686/cyxb2024024

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Effects of dietary supplementation with bile acid on ileal epithelial morphology, microflora composition, and relative transcript levels of IFN-γ in the ileal mucosa of goats with subacute ruminal acidosis

Yue CHEN(), Pin SONG, Man-man HOU, Xiao-ran YANG, Li-ping LIU, Ying-dong NI()   

  1. College of Veterinary Medicine,Nanjing Agricultural University,Key Laboratory of Animal Physiology and Biochemistry,Ministry of Agriculture and Rural Areas,Nanjing 210095,China
  • Received:2024-01-16 Revised:2024-03-11 Online:2024-12-20 Published:2024-10-09
  • Contact: Ying-dong NI

Abstract:

The aim of this study was to investigate the effect of dietary supplementation with bile acid on intestinal mucosal structure, intestinal microflora composition, and the relative transcript levels of IFN-γ (encoding interferon γand IfnGR1 (encoding the IRN-γ receptor)in the ileal mucosa of goats with subacute ruminal acidosis (SARA) induced by a high-concentrate diet. Fifteen 3-month-old male goats (mean weight, 18.19±2.83 kg) were selected and implanted with permanent rumen fistulas by surgery. After a 2-week recovery period, the goats were randomly divided into three groups: a control group (CON), a subacute ruminal acidosis group (SARA), and a SARA plus bile acids treatment group (SARA+BA), with five goats in each group. Goats in the CON group were fed with a low-concentrate diet (concentrate∶forage=3∶7), those in the SARA and SARA+BA groups were fed with a high-concentrate diet (concentrate∶forage=7∶3), and those in the SARA+BA group were fed with an additional 3 g of bile acid through the rumen fistula every day for 6 weeks. At the end of the experiment, the goats were slaughtered and the ileal epithelial tissues were sampled to analyze their morphology, the characteristics of goblet cells and paneth cells, and the transcript levels of IFN-γ and IfnGR1 in the mucosa. In addition, the ileal digesta were collected to analyze the composition of the microbial community. The results showed that, compared with the CON group, the SARA group showed an irregularly shaped brush border of the ileal epithelium, indicative of a degree of injury, but no significant difference in the number of cup cells and paneth cells in the villi and crypt (P>0.05). Compared with the CON group, in the SARA group, the transcript levels of IFN-γ and IfnGR1 in the ileum mucosa were decreased (0.05<P<0.1), the diversity of the microbial community (Ace and Shannon’s indexes) in the ileum contents was decreased (P<0.05), and the relative abundance of the phylum Firmicutes in the microbial community in the ileum was significantly increased (P<0.05). Compared with the CON group, the SARA group showed significantly lower relative abundance of Unclassified_f_LachnospiraceaeRuminococcus and Christensenellaceae_R-7_groupP<0.05) and significantly higher relative abundance of Erysipelotrichaceae_UCG-006 and Clostridium_sensu_stricto_1P<0.05) in the microbial community. Compared with the SARA group, the SARA+BA group had a smoother brush border of the ileal epithelium, the epithelial structure was complete, the villi height was significantly increased (P<0.05), and the number of paneth cells was significantly increased (P<0.05), but the number of cup cells in the villi and crypt was not significantly different (P>0.05). Also, compared with the SARA group, the SARA+BA group showed increased transcript levels of IFN-γ in the mucosa (0.05<P<0.1), increased transcript levels of IfnGR1P<0.05), significantly increased bacterial diversity (Ace index) in the ileum microbial community (P<0.05), and a lower relative abundance of the phylum Firmicutes (P<0.05). At the genus level, the beneficial bacteria Unclassified_f_LachnospiraceaeRuminococcus and Christensenellaceae_R-7_group were more abundant in the SARA+BA group than in the SARA group (P<0.05), and the harmful bacteria Erysipelotrichaceae_UCG-006 and Clostridium_sensu_stricto_1 were significantly less abundant (P<0.05). In conclusion, feeding bile acid to goats with subacute ruminal acidosis improved the morphology and structure of the ileum of SARA goats, alleviated the disturbance of the microflora in the ileum, and alleviated damage to the ileum mucosa of SARA goats by up-regulating the relative mRNA expression levels of anti-inflammatory factor IFN-γ and receptor IfnGR1 in the mucosa.

Key words: bile acid, subacute ruminal acidosis, ileal mucosa, microflora composition, goat