The hindgut epithelial barrier plays an important role in maintaining absorption and immune homeostasis in ruminants. However, little information is available on changes in colon epithelial barrier structure and function following grain-induced subacute ruminal acidosis (SARA). The objective of this study was to investigate the effects of grain-induced SARA on colon epithelial morphological structure, permeability, and gene expression involved in epithelial barrier function. Twelve mid-lactating (136 ± 2 d in milk; milk yield = 1.68 ± 0.15 kg/d) Saanen dairy goats with 62.13 ± 4.76 kg of body weight were randomly divided into either the control (CON) treatment (n = 6) or SARA treatment (n = 6). The CON goats were fed a basal diet with a nonfiber carbohydrates to neutral detergent fiber ratio of 1.15 for 60 d. The SARA goats were fed 4 diets with increasing nonfiber carbohydrates to neutral detergent fiber ratio at 1.15, 1.49, 2.12, and 2.66 to induce SARA, with each diet (referred to as period) being fed for 15 d, including 12 d for adaptation and 3 d for sampling. Continuous ruminal pH recordings were used to diagnose the severity of SARA. Additionally, colonic tissues were collected to evaluate the epithelial morphological structure, permeability, and expression of tight junction proteins using transmission electron microscopy, Ussing chamber, quantitative real-time PCR, and Western blotting. Profound disruption in the colonic epithelium was mainly manifested as the electron density of tight junctions decreased, intercellular space widened, and mitochondria swelled in SARA goats. Colon epithelial short-circuit current, tissue conductance, and the mucosal-to-serosal flux of fluorescein isothiocyanate-dextran 4 kDa were increased and potential difference was decreased in SARA goats compared with CON goats. Subacute ruminal acidosis increased mRNA and protein expression levels of CLDN1 and OCLN in the colonic epithelium. Overall, the data of the present study demonstrate that SARA can impair the barrier function of the colonic epithelium at both structural and functional levels, which is associated with severe epithelial structural damage and increased permeability and changes in the expression of tight junction proteins.

When subclinical ketosis (SCK) occurs in dairy cows, it leads to an excessive production of β-hydroxybutyrat (BHBA), which disrupts liver lipid metabolism and triggers a series of inflammatory responses. Rutin (RT), a flavonoid extracted from plants, exhibits diverse biological activities. However, its potential to mitigate BHBA-induced liver inflammation and lipid accumulation in dairy cows remains unexplored. In this study, we investigated the effect of RT on the BHBA-induced injury of hepatocytes and the possible mechanism. First, hepatocytes were treated with BHBA (0, 0.3, 0.6, 1.2, 2.4 mM) to assess its effects on inflammation impairment and lipid accumulation. Second, hepatocytes were pretreated with RT (0, 25, 50, 100, 150 μg/mL) to evaluate its protective effects. Third, hepatocytes were divided into five treatment groups: blank control, BHBA treatment, RT + BHBA treatment, NF-κB activator (PDTC) + BHBA treatment, and RT + PDTC + BHBA treatment. This experiment further explored the underlying mechanism of RT in mitigating BHBA-induced hepatocyte injury. The results demonstrated that RT at 100 and 150 μg/mL mitigated the increases in hepatocyte interleukin-1 beta (IL-1β), IL-6, triglyceride (TG), and total cholesterol (TC) contents induced by high concentrations of BHBA (p < 0.05). Compared to the BHBA treatment, 100 μg/mL RT significantly downregulated the relative protein expression of P-NF-κB p65 and the relative mRNA expression of NF-κB p65, tumor necrosis factor-alpha (TNF-α), IL-1β, IL-6, peroxisome proliferator-activated receptor gamma (PPARγ), and microsomal triglyceride transfer protein (MTP), while upregulating the relative mRNA expression of IKBα (p < 0.05). Additionally, these effects were more pronounced with the combined pretreatment of the PDTC and RT. In conclusion, RT inhibits BHBA-triggered hepatocyte inflammation and lipid accumulation by modulating the NF-κB signaling pathway, implying that RT may be a promising target for ameliorating damage in SCK cows.

The transition from late gestation to early lactation challenges antioxidant defense in dairy cows. Nutritional strategies that support antioxidant capacit