亚急性瘤胃酸中毒耐受性不同的奶牛瘤胃上皮形态及功能差异研究

Comparison of rumen epithelium morphology and function in dairy cows with differences in susceptibility for subacute ruminal acidosis

本试验旨在探究SARA(亚急性瘤胃酸中毒)耐受性不同奶牛的瘤胃上皮形态及其功能差异。选取12头装有永久性瘤胃瘘管的泌乳中期荷斯坦奶牛,饲喂精粗比为4∶6的日粮,并根据瘤胃pH值的高低,分为SARA易感组(SUS,n=4)和SARA耐受组(TOL,n=4)。瘤胃上皮形态及功能分析结果显示,与TOL组比较,SUS组奶牛瘤胃上皮的棘突层和基底层厚度明显增厚(P<0.05),SUS组奶牛瘤胃上皮组织中参与挥发性脂肪酸(VFA)吸收的PAT1、MCT4和DRA基因表达量较TOL组显著下调(P<0.05),而H^(+)转运载体NHE1、NHE2、NHE3和调节胞内pH的vH^(+)ATPase和Na^(+)/K^(+)ATPase的表达量显著升高(P<0.05);对参与调控瘤胃VFA代谢的基因定量结果表明,SUS组PDHA1和SREBP2的表达量显著高于TOL组(P<0.05),而HMGCL-2的表达量显著降低(P<0.05);此外,SUS组CDK2、CDK6和Cyclin D1、Bad及Caspase-9等参与瘤胃上皮细胞增殖与凋亡的基因表达量显著高于TOL组(P<0.05)。结果说明,在相同日粮条件下,SUS组奶牛瘤胃上皮细胞调控游离脂肪酸吸收的基因表达量下调,造成瘤胃上皮对VFA的吸收能力下降,使得瘤胃内VFA累积和pH下降,并导致SUS组奶牛SARA的患病风险增高。

This experiment was conducted to compare the morphology and function of rumen epithelium in dairy cows with differences in susceptibility to subacute ruminal acidosis(SARA).Twelve multiparous fistulated Holstein cows in mid lactation were housed in individual stalls and fed a diet with a concentrate to forage ratio of 4∶6 throughout the experimental period.Based on the ruminal pH,cows with relatively lower and higher mean ruminal pH were assigned,respectively,to susceptible(SUS,n=4)and tolerant(TOL,n=4)groups.The examination of ruminal epithelial morphology and function revealed that the cells in the spinous process and basal layer of ruminal epithelium were thicker in the SUS than in the TOL group(P<0.05).In the SUS group,the expression levels of PAT1,MCT4,and DRA genes involved in volatile fatty acid(VFA)absorption were significantly lower(P<0.05),while the NHE1,NHE2,NHE3,vH^(+)ATPase,and Na^(+)/K^(+)ATPase levels were significantly higher than in the TOL group(P<0.05).The results of gene expression for ruminal VFA metabolism showed that PDHA1 and SREBP2 in the SUS group was higher(P<0.05),while the expression of HMGCL-2 was significantly lower(P<0.05).In addition,the expression levels of genes involved in the proliferation and apoptosis of rumen epithelial cells,such as CDK2,CDK6,Cyclin D1,Bad and Caspase-9 in the SUS group were higher in the SUS group than in the TOL group(P<0.05).In summary,under the same diet,there was a lower expression of genes associated with free fatty acid absorption and a higher expression of genes related to non-free fatty acid absorption in rumen epithelial cells of SUS cows.This results in free fatty acid accumulation and reduced ruminal pH in the SUS group,and increased the risk of SARA in these cows.