为研究高剂量氧化锌对早期断奶仔猪肠黏膜屏障的影响并探讨其作用机理,选取54头21日龄断奶仔猪按胎次一致、体质量相近和公母各半方法分为3组,每组3个重复,每个重复6头.哺乳组仔猪继续哺乳至35日龄,基础日粮组饲喂基础日粮(110 mg·kg~(-1)锌),高锌组饲喂基础日粮+3 000 mg·kg~(-1)锌(氧化锌).分别于28和35日龄取样测定血浆D-乳酸、内毒素含量和二胺氧化酶(DAO)活性、肠系膜淋巴结细菌移位率以及结肠内容物大肠杆菌数,并分析回肠上皮细胞紧密连接蛋白Occludin和ZO-1的表达.结果显示:与哺乳组相比,断奶仔猪饲喂基础日粮,28日龄时血浆中D-乳酸、内毒素含量和DAO活性显著升高(P<0.05),至35日龄时,肠黏膜仍维持较高的通透性;添加高锌抑制上述3个指标的升高,进而阻止肠黏膜通透性的增加,达到与哺乳组相同的效果;与哺乳组相比,基础日粮组和高锌组在28和35日龄时均存在肠系膜淋巴结细菌移位现象,但是高锌组低于基础日粮组(P>0.05);28日龄时,基础日粮组结肠内容物大肠杆菌数大于哺乳组(P<0.05),与高锌组比较差异不显著(P>0.05),35日龄时各组间差异不显著(P>0.05);与哺乳组相比,仔猪断奶后饲喂基础日粮使Occludin和ZO-1mRNA丰度以及ZO-1的表达下降(P<0.05),高锌组Occludin和ZO-1 mRNA丰度、ZO-1蛋白表达均显著高于基础日粮组(P<0.05).结论:仔猪断奶后肠黏膜通透性增加,肠上皮细胞紧密连接蛋白表达下降;而添加高剂量氧化锌可抑制细菌在肠道黏膜上的黏附,阻止上皮细胞渗透性增加,能保护肠黏膜屏障功能.%To study the effect of high level of zinc oxide on intestinal mucosal barrier and its mech-anisms in early weaning piglets, 54 piglets, weaned at 21 d of age, were allocated into three treatments on the basis of similar BW, ancestry, and gender. Each treatment had three replica-tions of six pigs (half males and half females). The experimental treatments diets were basal diet and basal diet +3 000 mg·kg~(-1) Zn (ZnO), another treatment piglets were receiving sow milk with mother (control). Plasma D-lactate and endotoxin level, DAO activity, bacterial transloca-tion in mesenteric lymph nodes and colon E. coli were measured to evaluate the intestinal permea-bility at 28, 35 d of age, and the level of Occludin and ZO-1 expression were also detected. The results showed that plasma D-lactate and endotoxin level and DAO activity were significantly in-creased in piglets of basal diet compared to the control group (P<0.05) at 28 d. The three pa-rameters remained high at 35 d. There were no significant differences between the high zinc and the control (P>0.05). At 28 and 35 d, bacterial translocation in mesenteric lymph nodes of pig-lets with high zinc was lower than that of piglets with basal diet(P>0.05). Colon E. coli of pig-lets with basal diet was increased compared to the control group (P<0.05) at 28 d, but there were no significant difference between the high zinc and the basal diet (P>0.05). The parameters did not differ among three groups at 35 d (P>0.05). Compared with the control, Occludin and ZO-1 mRNA and ZO-1 expression was significantly decreased in the basal diet group (P<0.05) and the high zinc (P>0.05), but the parameters of piglets with high zinc was greater than that of basal diet (P<0.05). It is suggested that early weaned piglets was in stresses, increasing in-testinal permeability and decreasing the expression of tight junction protein Occludin and ZO-1, and these damage may be relaxed by diet supplementation with high level of zinc oxide, through inhibiting bacterial adhesion in the intestinal mucosa and preventing the increase in epithelial cells permeability.
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