【作者】 杨威；

【导师】 王哲；

【作者基本信息】 吉林大学 ， 临床兽医学， 2014， 博士

【摘要】 反刍动物围产期高发疾病将直接影响机体泌乳量，给养殖业带来巨大损失。围产期，又称为过渡期，通常为产前3周至产后3周的一段特殊时期。而这一时期由于动物体况、能量代谢和激素分泌调节改变导致干物质摄入下降，使机体处于能量负平衡状态，极易导致酮病及脂肪肝的发生。目前对围产期奶牛脂肪肝的发病机制研究较为详细，而对泌乳期绵羊的脂肪肝研究较少。奶牛脂肪肝是指干乳期过于肥胖的母牛产犊后能量负平衡，体脂动员所致发的一种以肝脏脂肪蓄积和脂肪变性为病理特征的围产期代谢病。多见于产乳量高的2-6胎经产牛，多发于日产奶30Kg以上高产牛，且常发生于泌乳的头2周。也有产犊前和产犊后1个月发病的。发病率一般为10%-50%，高发牛群可达50-90%，病死率为25%。奶牛脂肪肝不仅造成奶产量下降，又因其常常诱发皱胃变位、胎衣不下及生产瘫痪等其他围产期疾病，给奶牛业带来严重的经济损失。奶牛分娩后的几天或几周内由于体况、能量代谢和激素调节的改变导致奶牛干物质摄入下降。为满足泌乳初期的能量需求，机体动员妊娠期脂肪组织储备的能量。脂肪动员的结果导致血液循环中非酯化脂肪酸(NEFA)含量增高。在能量负平衡状态下大量NEFA在肝脏中经不完全氧化生成酮体或被再酯化生成甘油三酯，导致酮病、脂肪肝的发生。因此对脂肪肝及时诊断可为尽早制定治疗措施，及预防措施提供保障。迄今脂肪肝诊断的金标准依然是肝脏活体穿刺，但作为介入性检测方法，肝脏活检存在多个弊端，不宜用于临床检测。脂肪肝超声诊断是一种操作简便、费用低廉、无损伤的诊断方法，对肝脏脂肪变性检测灵敏度高。其原理是，疾病发展过程中可导致组织结构改变，将会引起超声信号变动，并在超声仪上显示出与正常结构相差异的图像。本研究旨在通过对泌乳初期的绵羊进行限饲管理，模拟自然状态的能量负平衡，复制脂肪肝病例，对脂肪肝超声图像特征分析，以建立绵羊脂肪肝超声诊断方法，为临床奶牛酮病及脂肪肝疾病诊断提供理论依据。本研究对分娩当天泌乳绵羊进行为期16天的限饲管理后成功建立绵羊脂肪肝模型。与对照组相比限饲哺乳绵羊血糖浓度下降明显，血液中NEFA及β-羟丁酸(BHBA)含量升高，表明限饲哺乳绵羊处于严重能量负平衡状态和明显的脂肪动员。同时血液中球蛋白、γ-谷氨酰转肽酶水平降低。限饲哺乳绵羊血液中甘油三酯、总胆固醇、低密度脂蛋白、胆红素、白蛋白、谷草转氨酶、乳酸脱氢酶含量增高。与对照组相比，限饲哺乳绵羊血液中高密度脂蛋白、谷丙转氨酶、碱性磷酸酶、胆碱酯酶、总蛋白含量明显差异，表明限饲羊存在一定程度的肝功能障碍。与对照组相比，限饲组绵羊催乳素、脂联素、瘦素的分泌量均高于正常组。通过对活体穿刺获取的肝组织进行甘油三酯含量测定，与对照组（甘油三酯含量小于2%）相比限饲哺乳绵羊肝脏呈现不同程度的脂肪浸润（4%-18.2%）。以肝脏甘油三酯含量小于2%（健康）、2%-5%（轻度脂肪肝）、5%-10%（中度脂肪肝）、10%-20%（重度脂肪肝）为标准对相应超声图像进行分组，分析不同组别超声图像中肝脏超声回声强度、肝肾回声强度比较、肝脏远场回声衰减程度、肝脏内血管壁清晰程度及血管壁边缘平滑度、肝脏与肠相邻边缘清晰可辨程度等特征。最终确定了超声探测部位为右侧第10-13三个肋间的肝脏超声区域，分别建立了健康、轻度、中度、重度脂肪肝3.5MHz及5MHz频率下超声诊断标准。三位观察者依照诊断标准对肝脏超声图像进行脂肪肝严重程度的评价及分类，结果表明：建立的5MHz超声诊断标准对正常，轻度、重度脂肪肝诊断的灵敏度较高，观察者间个案处理一致性较好；建立的3.5MHz超声诊断标准对正常、中度、重度脂肪肝诊断的灵敏度较高，对轻度脂肪肝诊断灵敏度仅37%，且观察者间对个案处理的一致性较低。综上所述，本研究建立的5MHz频率下超声诊断绵羊脂肪肝方法，对不同严重程度脂肪肝检测的灵敏度较高，可实施性较好。建立的3.5MHz频率下超声诊断绵羊脂肪肝方法，对中度及重度脂肪肝诊断灵敏度较高，可用于中度及重度绵羊脂肪肝的超声诊断。本研究为奶牛脂肪肝超声诊断提供了技术支持和理论依据。更多还原

【Abstract】 Perinatal period, also called transition period, is usuallydefinedfrom three weeks prior birth tothree weeks postpartum. During the perinatal period, the animals showed a bad body condition,changed energy metabolism and hormone secretion and a decreased dry substancethat highincidencediseases of ruminant, such as ketosis and fatty liver, were caused and have a directinfluence on milk yield. Currently, the pathogenesis of dairy cow fatty liver has beendetailedrepresent, while the research of fatty liver on lactation period sheep was less. Fatty Liverin dairy cow is usually developed after parturition and caused by negative energy balance(NEB) ofporkycow. To respond theNEB, number of adipose in dairy cows was oxydated that cause asteatosisLiver. Fatty Liver was usually developed inhigh-yielding dairy cows during2weeklactational, and has a high disease rate10%-50%and fatality ratio25%. Fatty Liver in dairy cowcan both cause a descended milk yield and inductothers disease, such as abomasum addendum.During the parturition period, dairy cow was undergoinga change of body condition, energymetabolism and hormonal, and leading toa decreaseddry matter intake.To deal with NEB, numberofadipose in dairy cows was decimposed that causes a great quantity non-esterified fatty acid(NEFA) in liver,and caused ketosis and fatty liver. Further evaluation of fatty liver is importantbecause of the risk of progressive liver disease. Liver biopsy is the gold standard for theassessment of fatty liver. As an invasive procedure, Liver biopsyhas several limitations, thatit isnot always achieved. Ultrasonography is a comparatively cheap, convenient, and noninvasivetesting, and has a high sensitivity of ultrasonographyin detecting hepatic steatosis. The principle ofultrasonography for evaluation liver disease is that if disease processes affect the structure of thetissue, the tissue should reflect an altered ultrasound signal, which will in turn give in texturefeatures value different to the normal tissue.In this research, postpartum sheep was managed witha restricted feeding to developraw state fatty liver. A method of ultrasonographic evaluation offatty liver in sheep was developed by analyzing the features of ultrasound imagesof fatty liver insheep, which also have a role of reference for fatty Liver dairy cow.In this research, a fatty liver model of parturition sheep was developedthrough16daysdietary restriction. Compared to control, the fatty liver sheep had a low blood level of glucose,globulose, glutamyltranspeptidase, and high BHBA, NEFA, triglyceride, bilirubin, low density lipoprotein, albumin, glutamic-oxal(o)acetic transaminase and lactate dehydrogenase, but therewere non difference in high density lipoproteins, alanine transarninase, alkaline phosphatase,cholinesterase, total proteinin plasma, thatsuggested a hepatosis.Compared to the control, therehad high secretion ofprolactin, adiponectin and leptinin plasmathe dietaryrestrictionlactationsheep.Compared to the control, the dietary restrictionlactationsheep have asevere triglycerideaccumulation. Following the grades of triglyceride, the ultrasoundimagesfeatures offatty liver sheep were obtained in right10-13intercostal of sheep anddeterminedby analyzeing the liver echo intensity, the ratio of liver and kidney, echo attenuation infar-field, the featuresof intestines, rumen wall and vessel wall in liver. As the result, the methodsof ultrasonographic evaluation of fatty liver in sheep by3.5MHz and5MHz probe was developed,respectively.With the analysis ofthreeobservers, there was a highsensitivity of ultrasonographic evaluationof difference levels fatty liver in sheep and the interobserver agreement wasgood by5MHzprobeultrasonography. While ultrasonographic evaluation of difference levels fatty liver by using3.5MHz probe had a moderate intraobserveragreement and only have a highsensitivity in detectingmidrange and severe fatty liver in sheep. This researchprovides a technology and theory forultrasonography in Fatty Liver of dairy cow.更多还原