Abstract: In order to investigate the effects of feeding high concentrate diets on the functional status of ruminal epithelia in terms of oxidative stress and cholesterol metabolism, seventeen lactating goats with similar body weight and milk production were randomly divided into three groups, including LC (n=5), HS (n=5) and HL (n=7) groups, which were fed by diets of concentrate∶forage of 35∶65 for whole experiment period (LC), concentrate∶forage of 65∶35 for 4 weeks (HS), and concentrate∶forage of 65∶35 for 19 weeks (HL), respectively. At the end of the experiment, ruminal epithelial tissues were sampled, promptly immersed in liquid nitrogen and then stored at -80 ℃ for analysis. The results showed that mRNA expression of the CDK2 and CDK4 genes related to cell cycle significantly increased in both HS and HL goats (P<0.05). The level of p-ERK1/2 proteins increased in HS but not in HL goats (P<0.05). However, GPR41 and 43 protein expression in the ruminal epithelium was not changed both in HS and HL compared to LC. The expression of the Casepase9 gene participating in cell apoptosis was significantly up-regulated in the HL and HS groups, while the anti-apoptotic index of the relative ratio of Bcl-2/Bax mRNA expression showed a tendency to decrease in the HS group compared to LC group (0.05<P< 0.1). In addition, the enzyme activity of SOD and CAT in the epithelium significantly increased in HL and HS goats compared to LC goats (P<0.05), whereas the total anti-oxidative capacity (T-AOC) increased only in HS goats (P<0.05). The level of cholesterol in ruminal epithelium significantly decreased in the HS group (P<0.01), and also showed a decreasing trend in the HL group (P=0.06). The enzymes ACAT1 and 2, which may be involved in the regulation of cholesterol metabolism, significantly increased in HL and HS goats compared to LC goats (P<0.05). Correlation analysis revealed that cholesterol concentration in the ruminal epithelium was negatively correlated with ACAT1 and ACAT2 mRNA expression in the HS group (P=0.0067, r=-0.8208; P=0.0100, r=-0.7980). Compared with the LC group, mRNA expressions of AE2, DRA, NHE2, NHE3 and νH⁺ ATPase genes involving VFAs transportation significantly increased (P<0.05), while NHE2 protein expression was not altered both in HS and HL groups. Compared with the HL group, the HS group’s T-AOC significantly increased (P<0.05) and the level of cholesterol significantly decreased (P<0.05). These results indicate that feeding high concentrate diets over a short time period can improve the health status and functions of ruminal epithelium, while feeding high concentrate diets over a longer period might lessen these beneficial effects.