PDF(Pubmed)
Abstract：
The ecosystem of ruminal microbiota profoundly affects the health and milk production of dairy cows. High-concentrate diets are widely used in dairy farms and evoke a series of metabolic disorders. Several studies have reported the effects of high-concentrate diets on the ruminal microbiome, while the effect of changes in ruminal microbial flora, induced by high-concentrate diet feeding, on the liver of dairy cows has not been studied before. In this study, 12 mid-lactating Holstein Friesian cows (weight of 455 ± 28 kg; parities of 2.5 ± 0.5; starting milk yield of 31.59 ± 3.2 kg/d; DMI of 21.7 ± 1.1 kg/d; and a DIM at the start of the experiment of 135 ± 28 d) were fitted with ruminal fistulas, as well as with portal and hepatic vein catheters. All cows were randomly divided into 2 groups; then, they fed with low-concentrate diets (LC, concentrate: forage = 40:60) and high-concentrate diets (HC, concentrate: forage = 60:40) for 18 weeks. The forage sources were corn silage and alfalfa hay. After the cows of two groups were euthanized over two consecutive days, ruminal microbiota; the concentration of LPS in the rumen content; cecum content; the levels of blood and histamine in rumen fluid, blood, and the liver; the histopathological status of the rumen and cecum; and the inflammatory response of the liver were assessed in dairy cows under conditions of subacute ruminal acidosis (SARA). These conditions were caused by high-concentrate diet feeding. All data were analyzed using the independent t-test in SPSS. The results showed that high-concentrate diet feeding increased the concentration of LPS and histamine in the rumen and plasma of veins (p < 0.05). The abundance of Bacteroidetes at the phylum level, and of both Bacteroidetes and Saccharibacteria at the genus level, was decreased, while the abundance of Firmicutes at the phylum level and Oscillibacter at the genus level was increased by high-concentrate diet feeding. The decreased pH values of ruminal contents (LC = 6.02, HC = 5.90, p < 0.05) and the increased level of LPS in the rumen (LC = 4.921 × 105, HC = 7.855 × 105 EU/mL, p < 0.05) and cecum (LC = 11.960 × 105, HC = 13.115 × 105 EU/mL, p < 0.01) induced the histopathological destruction of the rumen and cecum, combined with the increased mRNA expression of IL-1β (p < 0.05). The histamine receptor H1R and the NF-κB signaling pathway were activated in the liver samples taken from the HC group. In conclusion, the elevated concentrations of LPS and histamine in the gut may be related to changes in the ruminal microbiota. LPS and histamine induced the inflammatory response in the ruminal epithelium, cecum epithelium, and liver. However, the cause-effect mechanism needs to be proved in future research. Our study offers a novel therapeutic strategy by manipulating ruminal microbiota and metabolism to decrease LPS and histamine release and to improve the health of dairy cows.
摘要：
瘤胃微生物群生态系统深刻影响奶牛的健康和产奶量。高浓缩饮食在奶牛场中广泛使用，并引起一系列代谢紊乱。一些研究报道了高浓缩饮食对瘤胃微生物组的影响，而瘤胃微生物区系变化的影响，高浓缩饮食诱导，关于奶牛肝脏的研究以前没有。在这项研究中,12头泌乳中期的荷斯坦弗里斯奶牛（体重455±28千克；平均为2.5±0.5；起始产奶量为31.59±3.2千克/天；MDI为21.7±1.1千克/天；实验开始时的DIM为135±28天）装有瘤胃瘘，以及门静脉和肝静脉导管。将所有奶牛随机分为2组；然后，他们用低精矿饮食喂养(LC，浓缩物：牧草=40：60）和高浓缩物饮食（HC，浓缩物：饲草=60：40）持续18周。饲草来源为玉米青贮和苜蓿干草。两组奶牛连续两天实施安乐死后,瘤胃微生物群；瘤胃内LPS含量；盲肠含量；瘤胃液中血液和组胺水平，血,和肝脏；瘤胃和盲肠的组织病理学状态；以及在亚急性瘤胃酸中毒（SARA）条件下评估奶牛的肝脏炎症反应。这些情况是由高浓缩饮食引起的。所有数据采用SPSS中的独立t检验进行分析。结果表明，高浓缩饲料喂养增加了瘤胃和静脉血浆中LPS和组胺的浓度（p<0.05）。在门水平上有大量的拟杆菌,以及属水平的拟杆菌和糖杆菌，减少了，而高浓缩饮食增加了门水平的Firmicutes和属水平的Oscillibacter的丰度。瘤胃内容物的pH值降低（LC=6.02，HC=5.90，p<0.05），瘤胃中LPS水平升高（LC=4.921×105，HC=7.855×105EU/mL，p<0.05）和盲肠（LC=11.960×105，HC=13.115×105EU/mL，p<0.01）诱导瘤胃和盲肠的组织病理学破坏，IL-1βmRNA表达增加(p<0.05)。在取自HC组的肝脏样品中,组胺受体H1R和NF-κB信号通路被激活。总之,肠道内LPS和组胺浓度的升高可能与瘤胃微生物群的变化有关。LPS和组胺诱导瘤胃上皮炎症反应，盲肠上皮,还有肝脏.然而,其因果机制有待进一步研究证实。我们的研究提供了一种新的治疗策略，通过操纵瘤胃微生物群和代谢来减少LPS和组胺的释放，并改善奶牛的健康。
