本试验旨在研究亚急性瘤胃酸中毒( SARA)对瘤胃上皮形态结构和通透性的影响。选用体况良好、体重相近的泌乳期萨能奶山羊9只,随机分为3组(对照组、SARA组、恢复组, n=3),对照组饲喂基础饲粮[非纤维性碳水化合物与中性洗涤纤维比(NFC/NDF)=1.40],SARA组和恢复组先后饲喂NFC/NDF为1.40、1.79、2.31、3.23的4种试验饲粮诱导SARA发生,每种饲喂15 d,恢复组奶山羊待SARA诱导成功后自由采食青干草30 d。对照组奶山羊分别在饲养30、60(与SARA组3只同时)和90 d(与恢复组3只同时)各屠宰1只。采集瘤胃腹囊部上皮组织用于石蜡切片、透射电子显微镜观察及尤斯灌流系统( Ussing chamber)研究。结果表明：1)组织切片结果显示,瘤胃上皮角质层厚度SARA组显著高于对照组和恢复组(P<0.05),恢复组显著低于对照组( P<0.05)；颗粒层厚度对照组显著高于SARA组和恢复组( P<0.05),但SARA组和恢复组之间无显著差异( P>0.05)；棘突层厚度3组之间无显著差异( P>0.05)；上皮总厚度恢复组显著低于对照组和SARA组(P<0.05),但对照组与SARA组之间无显著差异(P>0.05)。透射电子显微镜结果显示,SARA组瘤胃上皮紧密连接被破坏,细胞间隙增大,棘状层细胞线粒体出现降解并出现空泡。2)与对照组相比,SARA组和恢复组瘤胃上皮短路电流( Isc)、组织导电性(Gt)和辣根过氧化物酶(HRP)流速显著升高(P<0.05),跨膜电位差(PD)显著降低(P<0.05)。综合得出,SARA破坏了奶山羊瘤胃上皮形态结构的完整性,使瘤胃上皮通透性增加,导致瘤胃上皮屏障功能长期受损。%The objective of this experiment was to study the effects of subacute ruminal acidosis ( SARA) on ruminal epithelial morphology and permeability in dairy goats. Nine healthy lactating Saanen dairy goats with similar body weight were randomly divided into three groups ( control group, SARA group and recovery group, n=3) . Dairy goats in control group were fed a basal diet [ non-fibre carbohydrates/neutral detergent fi-bre ( none fiber carbon NFC/NDF)=1.40] , those in SARA group and recovery group were fed experimental diets with different NFC/NDFs (1.40, 1.79, 2.31 and 3.23 in order, each for 15 days), which gradually in-duced SARA, and those in recovery group were ad libitum fed green hay for 30 days after SARA. One of 3 goats in control group were slaughtered on days 30, 60 ( together with 3 goats in SARA group) and 90 d of feeding ( together with 3 goats in recovery group) , respectively. Samples of the ruminal epithelium from ven-tral sac were collected to make paraffin section, observe under transmission electron microscope and do Ussing chamber analysis. The results showed as follows:1) the results of histological slice revealed that the thickness of ruminal epithelial stratum corneum in SARA group was significantly higher than that in control and recovery groups ( P<0.05) , and recovery group was significantly lower than control group ( P<0.05);the thickness of granulosum stratum in control group was significantly higher than that in SARA and recovery groups ( P<0.05) , but there was no significant difference between SARA group and recovery group ( P>0.05);the thick-ness of spinosum stratum in three groups had no significant difference ( P>0.05);the total thickness of the ru-men epithelium in recovery group was significantly lower than that in control and SARA group ( P<0.05) , but there was no significant difference between control and SARA groups ( P>0.05) . The results of transmission e-lectron microscope showed rumen epithelial tight junction structure in SARA group was destroyed and intercel-lular space was increased, and spinosum stratum cell mitochondria was degraded and showed vacuoles. 2 ) Compared with control group, the short-circuit, tissue conductance and the flux rate of horseradish peroxidase of rumen epithelium in SARA and recovery groups were significantly increased ( P<0. 05 ) , and potential difference was significantly decreased ( P<0.05) . In conclusion, SARA impairs the integrity of ruminal epithe-lial morphological structure in dairy goats, and causes an increase in ruminal epithelial permeability, which re-sults in rumen epithelial barrier function long-term damage.
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