【作者】 谷子林；

【导师】 霍贵成；

【作者基本信息】 东北农业大学 ， 动物营养与饲料科学， 2004， 博士

【摘要】 伴随着规模化养兔的开展,家兔疾病呈现上升势头。尤其是断奶仔兔的肠炎和腹泻,成为一些兔场的最主要疾病。一些技术储备不足的兔场,幼兔死亡率高达50%～70%,其中腹泻占到80%以上。生产中采用传统方法以抗生素等药物控制腹泻,不仅造成药物的残留,对人体健康造成威胁,同时带来一系列的弊端。家兔腹泻病因复杂,患病后治愈率较低,因此,成为中国养兔业的棘手问题,也是世界养兔业的技术难题之一。 为了深入探讨断乳仔兔腹泻发生诱因和机制,并以生物活性物质替代抗生素防治该病,本课题从三个方面开展了研究工作:第一,断乳仔兔腹泻的诱因研究。根据广泛的生产调查、多年的实践经验和国内外文献的查询,确定四大诱因,即低纤维日粮、抗生素诱发、饲料应激和病原菌污染;第二,发病和死亡机理研究,进行了盲肠区微生物的变化、血液生理生化指标的测定、肠道pH和内容物的变化、消化道组织病理变化的研究;第三,断乳仔兔腹泻的生物调控研究。在营养调控的基础上,开展双岐杆菌制剂调控、复合微生态制剂调控、寡糖和大蒜素调控等。拟通过三个方面的研究,实现三个目标:确定发病诱因,明确致病机理,探索生物调控途径。最终使断乳仔兔腹泻得到有效控制。 研究表明: 1.低纤维日粮(CF7%和CF9%)可导致断乳仔兔发生腹泻。粗纤维含量与腹泻频率呈负相关,即粗纤维含量越低,腹泻频率越高。从日增重、料重比、营养物质消化率等几项指标综合评价,断乳仔兔日粮适宜的粗纤维含量为12%。 2.低纤维日粮型腹泻断乳仔兔盲肠内容物中无氮浸出物含量有一定增加,部分支持了Cheeker和Patton的“后肠碳水化合物过度负荷”学说。但在严格控制环境卫生和球虫病的条件下,低纤维日粮使断乳仔兔仅发生粘液性肠炎。结合本研究其他信息认为:低纤维日粮使断乳仔兔消化道内环境(盲肠内淀粉含量、VFA、pH等)发生一定变化,有利于病原菌(如沙门氏菌、大肠杆菌、魏氏梭菌等)的侵入和增殖,改变了正常的微生物菌群,使断乳仔兔处于一种亚临床状态。当卫生不良、球虫侵袭、环境应激等情况发生时,容易爆发急性肠炎或腹泻。 3.低纤维日粮、饲料污染、饲料突变和大剂量饮用氨苄青霉素均可诱导断乳仔兔发生腹泻。每只断乳仔兔每天食入0.2克腹泻患兔盲肠内容物(含有大肠杆菌63 2000个,魏氏梭菌79 600个),腹泻率达到45%(CF14%日粮)～80%(CF12%日粮);每天每只口服60万单位氨苄青霉素,可使腹泻率达到75‰以CF10%和CF14%日粮交替更换,可使100%断乳仔兔发生腹泻。四种因素是生产中断乳仔兔腹泻的主要病因。 4.低纤维日粮使双歧杆菌、拟杆菌、乳酸杆菌和消化球菌等有益菌含量大幅度降低,大肠杆菌和沙门氏菌增加,正常微生物菌群失调。据此提出健康断乳仔兔最佳菌群比:双歧杆菌、拟杆菌、乳酸杆菌、消化球菌与大肠杆菌的比值分别为17:1、100:1、12:1和20:1;饲料污染、饲料突变、氨苄青霉素诱导的断乳仔兔腹泻,盲肠内以上几种有益微生物大幅度减少,以氨苄青霉素组减少幅度最大,其次是饲料污染和饲料突变组。大肠更多还原

【Abstract】 The enteritis and diarrhea of the weanling rabbits have become a big problem when the number and the size of the warren have been increased in china, especially, for the poor management practices farms in our country, the mortality of young rabbit reaches 50%~70% , 80 percent of which is diarrhea disease-causing. During farm operations, antibiotics generally are used to treat the diarrhea, which not only results in drug residues in meat or milk, but also have negative effect on the rabbits Solving the big problem of the warren has become a research interest due to the possible health benefits afforded humans consuming meat.Our objectives were to determine the mechanism and pathogenesis of the weanling diarrhea and find bio-active substances to substitute for antibiotics. Three trials were involved in the research: First, ascertain the diarrhea pathogenesis for weanling rabbits that were low fiber level in diet, antibiotics-inducing, stress of feed change and pathogen contaminated; Secondly, discussing the mechanism of the weanling diarrhea including its beginning, development and animal’s death, according to the change of cecum microorganism, test for blood physiological and biochemical index, the change of pH value and content of alimentary tract; Thirdly, to ensure the diarrhea can be effectively controlled, three fields were planed to study and reached such targets that the nosogenesis can be determined, pathogenesis found, and biological regulating way, according to further nutritional regulating ways that included Bifidobacterium preparation, complex preparation of probiotics, oligosaccharides, allitridum and so on.Analysis of dietary data suggested the correlation between fiber level in diet and the incidence of the diarrhea is negative. The diarrhea can be induced for the weanling rabbit fed the diet with low fiber levels (CF7% and CF9%). The 12% fiber level in ration for the weanling rabbit was recommended considering the gain per day, the ratio of feed to weight, nutrients digestive rate etc.The nitrogen free extract increased in cecum content to some extent for the weanling rabbit having diarrhea induced by low fibber diet, which partially supports Cheeker-Patton theory "intestine overload of carbohydrate", but in the condition of strict controlling sanitary environment and coccidiosis, only did the mucous enteritis happen with low fiber diet. We believed some changes occurs in the digestive tract (the starch contents in cecum, VFA, pH etc.) under the low fiber diet condition, which led that the animal was more susceptible to pathogens (salmonella, colibacillus and Clostridium perfringens etc.) infection and proliferation, and normal microbial clump had altered, which made the weanling rabbit sub-clinical state. The enteritis and diarrhea would erupt under the circumstance of poorsanitary environment, cocci to invade and external stress.The diarrhea can be induced for the weanling rabbits by low fiber diet, feed contaminated and feed abruptly altered or ampicillin drinked with large dosage. The diarrhea incidence reached from 45% (when CP/o diet fed) to 80% (when CP/o diet fed) as we fed the every weanling rabbit 0.2g /d cecum contents of the ill (contained colibacillus 632000 pfu, Clostridium perfringens 79600 pfu); The diarrhea incidence can reach 75% to 100% with the oral dosage 600KJU/day/rabbit ampicillin; the diarrhea occurred for all rabbit when two diets changed alternatively between CF10% and CF14%. Four factors above were main reasons to diarrhea of the weanling in rabbitry.The diet with low CF led to a severe decrease in the amount of useful microorganism including Bifidobacterium, Bacteriodes, lactobacillin and digestive cocci, and a increase in the amount of colibacillus and salmonella, an disorder in normal flora. It was concluded that the optimal flora ratio of Bifidobacterium, Bacteriodes, lactobacillin and digestive cocci to E. coli for healthy weanling rabbit were 17:1, 100:1, 12:1 and 20:1, respectively. The diarrhea can be induced by feed contaminated and abrupt change or ampicillin for the weanling rabbit, and the beneficial microorganism above decreased greatly in cecum, those adverse effects ampicillin brought most, and sequentially the feed contaminated, feed abrupt change. The harmful microorganism such as E.coli and Clostridium perfringens increased markedly. The benefitful microorganism was related negatively to the harmful. Intestinal flora disorder resulted from the different factors was main reason for diarrhea.The pH value in digestive tract increased usually when rabbit suffered from diarrhea, which was not only the result of digestive disorder, and signs of intestinal microbial disorder. It supplied better environment for the proliferation of the harmful microorganism.For diarrhea resulted from low fiber diet, probiotics made the best curable effect, EM, ollicin and olligofuctose in sequence. No co-operated effect existed between two active substances between probiotics, ollicin and olligofuctose to prevent the illness. It had different effects for diarrhea caused by different factors, which decreased diarrhea rate induced by ampicillin and polluted feed at 15%, 20 to 40%, respectively. It suggested that 0.2% probiotics prevent the weanling rabbit from diarrhea induced by feed abrupt change. The research can supply theoretic and practical support for safe rabbits production.The probiotics and bifidobacterium ado lescentis had special effects on diarrhea resulted from low fiber diet with 98% and 100% curable rate. It produced certain effect on the illness by abrupt change in feed, polluted feed and ampicillin with different addition level of probiotics, and the curable rate was related to dosage. When 7.5 ml probiotics was injected per rabbit each time, the cure rate of three kinds of diarrhea was 76.92%, 68.18% and 0.71%, respectively. The research can supply theoretic and practical evidence for antibiotics replaced by probiotics in rabbit and others.Such serum indices for the ill rabbit increased as alkaline phosphatase, glutamic-oxalacetictransaminase (GOT), glutamic-pyravatic transainase (GPT) and urea nitrogen to some degree compared with the healthy; The more serous diarrhea was, the more severely the viscera of rabbits damnified, further the serum indices ascended. So these can be a sort of signs of weanling rabbit’s organ damnification as a biological diagnosis way.The author made a series of pathology image by systematical study on pathogen dissection and nosogenesis regulation to provide reference to diagnosis of diarrhea.更多还原