【作者】 苑学；

【导师】 王哲；

【作者基本信息】 吉林大学 ， 临床兽医学， 2011， 博士

【摘要】 近年来,精饲料的大量使用极大地提高了反刍动物的生产性能,但同时也增加了营养代谢疾病特别是瘤胃酸中毒发生的几率。肉牛患亚急性酸中毒的发病率超过15%,牛群的年淘汰率常高达45%。美国每年仅肉牛肥育过程中因瘤胃酸中毒造成的直接经济损失就高达0.6¹亿美元。由于亚急性瘤胃酸中毒除采食量下降和增重缓慢外不表现明显的临床症状,严重制约了该病的诊断和防治。本实验在应用末端限制性片段长度多态性分析（T-RFLP）技术和荧光定量PCR技术对不同pH值肉牛瘤胃微生物区系进行分析的基础上,运用瘤胃微生态理论、细菌代谢工程策略,以乳酸利用菌和酵母复合调控瘤胃乳酸的分解、利用为技术核心,研制肉牛亚急性瘤胃酸中毒微生态制剂,为防治肉牛亚急性瘤胃酸中毒开辟一条新的途径。本试验表明,育肥牛采食大量精饲料可使瘤胃pH≤5.8,瘤胃中的反刍月形单胞菌数量显著减少,但埃氏巨型球菌的数量显著增加,乳酸杆菌数量显著增加;瘤胃中的乙酸浓度显著减少,丙酸、丁酸浓度变化不明显,乳酸浓度显著增加。肉牛亚急性瘤胃酸中毒的病理基础是瘤胃乳酸蓄积。通过血气指标测定发现,肉牛轻度和中度亚急性瘤胃酸中毒时,血液PCO₂以及HCO₃^-浓度显著降低,表明机体碱储备不足,缓冲能力下降,存在代偿性酸中毒;同时根据水合状态和血象指标,病牛存在轻度脱水和炎性反应。体外试验表明,筛选出酿酒酵母、产朊假丝酵母和热带假丝酵母与反刍月形单胞菌、埃氏巨型球菌的最优酵母组合,该微生态制剂可以提高反刍月形单胞菌、埃氏巨型球菌利用乳酸的能力,促进乳酸的利用和分解在体试验证实,健康肉牛灌服复合瘤胃微生态制剂后,临床检查、血液生化指标分析未见异常,说明该微生态制剂安全、无毒、可靠。亚急性瘤胃酸中毒的肉牛灌服复合微生态制剂后,加速瘤胃内的乳酸的分解利用,降低瘤胃内的乳酸浓度,缓解乳酸的蓄积。初步证实该微生态制剂对肉牛亚急性瘤胃酸中毒具有良好的治疗效果。更多还原

【Abstract】 In recent years, increasing more concentrated feed could increase animals’production performance, at the same time, this bring about a risk of nutritional and metabolic diseases, especially rumen acidosis. Acute acidosis often causes animals’death. An incidence of sub-acute acidosis in beef is over 15%. The elimination rate of sub-acute acidosis in herd is more than 45% per year. In America, the direct economic loss caused by rumen acidosis in the fattening of beef is up to 0.6 to 1 billion dollars every year. Sub-acute rumen acidosis often occurs in the last stage of beef fattening.The striking decrease and an irregular undulate change of feed intake will lead to a decrease of production performance and feed conversion rate when the chronic acidosis happens. So diagnosis,prevention and cure is a key problem for sub-acute rumen acidosis in beef.This experiment develops a compound microbial pharmaceutics for subacute rumen acidosis in beef cattle though analysising the microfloras in different pH value of rumen in beef cattle and using T-RFLP and PCR technology with rumen micro-ecological theory, bacteria metabolic engineering strategy and the change of rumen function as the theoretical basis, and with the compound of lactic acid bacteria and yeast as the core technology. This will open up a new way for the prevention and control for rumen subacute acidosis in beef cattle.This experiment found when feeded with concentrated feed, the rumen selenomonas ruminantium significantly reduced, but megasphaera elsdenii and lactobacillus increased significantly (P<0.01); acetic acid concentration in the rumen significantly reduced (P<0.05), the change of propionic acid and butyric acid concentration is not obvious ( P>0.05 ) , lactic acid concentration increased significantly and accumulated in the rumen, that will cause subacute rumen acidosis.Through the determination of blood gas index and ion concentration we found that the PCO2 and the concentration of the Na2HCO3 in blood decreased with the decrease of the pH in the rumen of beef cattle with mild and moderatly subacute rumen acidosis, this suggest that a growing concentration of hydrogen ions in the blood was beyond the action of HCO3-buffer, the dynamic balance system of pH had been destroyed, subsequently resulted in compensative metabolic acidosis. A large number of lactic acide accumulated in the rumen leaded to body dehydration, secondary inflammation wich was characterized by an increase of the number of white blood cells. The decrease in the number of eosinophilic white blood cells suggested that toxic substances like histamine etc. might exist in the boody, especially the rumen. Neutrophils increased, lymphocytes decreased relatively with the nuclear type of neutrophils shifted to the left obviously, this is an important character of rumen acidosis.Screening the best yeast combination from saccharomyces cerevisiae, candida utilis, tropical candida with selenomonas ruminantium and megasphaera elsdenii, a rumen compound probiotics for sub-acute rumen acidosis of beef cattle was developed successfully. The probiotics can promote the use of lactic acid by candida utilis, tropical candida combined with selenomonas ruminantium and megasphaera elsdenii, restrain the further accumulation of lactic acid in vitro.The health beef cattle administered with the composite rumen probiotics had no change of analysising the blood biochemical index and testing the body metabolic function, which suggested that the composite rumen probiotics is safe non-toxic and reliable for beef cattle.When administered with the probiotics to the beef cattle with subacute rumen acidosis, the concentration of lactic acid in the rumen was decomposed and utilized, and returned to normal level fastly within 24h post-treatment. This initially proved that the probiotics is effective for subacute rumen acidosis of beef cattle.It is conclude that sub-acute rumen acidosis results from the accumulation of lactic acide in the rumen with the decrease of lactic acide–utilizing bacteria selenomonas ruminantium and the increase of lactic acide–generating bacteria lactobacillus. The probiotics combined saccharomyces cerevisiae, candida utilis, tropical candida with selenomonas ruminantium and megasphaera elsdenii is effective for subacute rumen acidosis of beef cattle through accelating the utilization of lactic acide in the rumen.更多还原