青贮接种乳酸菌与绵羊瘤胃菌群的互作及其对粘膜免疫的作用机制研究

Lactic acid bacteria (LAB) is the most common additive in silage, besides improving silage fermentation quality and aerobic stability, it can promote animals weight gain and production performance. However, its function is affected by the factors such as region, raw material and season. We have isolated thousands of LAB strains from the local cattle and sheep digestive tract and fermented feed, ten alternate strains were screened by antibacterial test. In addition, five strains were selected by comprehensive comparison for silage addition tests of whole crop corn, sorghum and Pennisetum giganteum, and it was found that the selected strains all improved the fermentation quality and aerobic stability of three raw materials. So does the addition of LAB to silage affect the performance of local sheep? What is the interaction pattern between silage LAB and different parts of the rumen microflora and its effect on the mucosal immune function of animals? In order to answer the above questions, this study will select 4 types of LAB to inoculate corn silage, and feed sheep after 90 days. To observe survival of silage LAB in the rumen and the interaction with rumen liquid phase, solid phase and rumen epithelium microflora. Investigate immune factors in blood and digestive tract mucosal samples before and after silage feeding, solve the fate of silage additives LAB in the animal digestive tract and its impact on animal immune function.

乳酸菌是青贮最常用的添加剂，改善青贮发酵品质和有氧稳定性外，对动物的增重和生产性能有促进作用。但其作用受地域、原材料和季节等因素的影响。我们从本地牛羊消化道和发酵饲料中分离了上千株乳酸菌，通过抗菌性等试验筛选了10株候补菌株。综合对比筛选5株做了全株玉米、高粱和巨菌草三种原料青贮添加试验，发现所选菌株不同程度改善发酵品质和有氧稳定性。那么乳酸菌添加青贮饲料对本地绵羊的生产性能是否有影响？青贮接种乳酸菌与绵羊瘤胃不同部分固有菌群的互作模式及其对粘膜免疫功能的影响又是什么样的？为了回答上述问题，本研究拟选择4种乳酸菌接种至玉米青贮，保存90d后饲喂绵羊。观察青贮接种乳酸菌在瘤胃中的生存性及与瘤胃液相、固相和瘤胃壁附着菌群间的互作关系。检测饲喂青贮饲料前后动物血液和消化道粘膜样品中免疫相关因子的含量，解析乳酸菌青贮添加剂在动物消化道中的命运及其对动物免疫功能的影响。

青贮饲料作为反刍动物优质粗饲料在世界各地被广泛制作和应用。乳酸菌是最常用的青贮添加剂，可以改善发酵品质和有氧稳定性，且有些乳酸菌添加剂对动物的增重和生产性能等有促进作用。但其作用受地域、原材料和季节等因素的影响。我们从本地牛羊消化道和发酵奶中分离了乳酸菌，通过抗菌性、药敏性、耐酸碱和粘附性等特征筛选了4株优势菌株。经筛选菌株添加至全株玉米、高粱和巨菌草三种原料青贮，发现所选菌株不同程度改善发酵品质和有氧稳定性。因在中其效果不如植物乳杆菌(LP)和布氏乳杆菌(LB)，研究青贮饲料中接种乳酸菌对绵羊消化道细菌群落及代谢产物的影响时我们选择了LP和LB。选取24只地方杂交绵羊，随机分为4组，分别饲喂玉米秸秆(S)、玉米秸秆青贮饲料、添加LP和LB的玉米秸秆青贮饲料。结果表明，与对照组和LB组相比，LP显著提高了青贮干物质(DM)含量，pH值显著高于LB组，好氧稳定性显著低于LB组。厚壁菌门和拟杆菌门是绵羊消化道两个优势门菌群。与玉米秸秆相比，饲喂玉米秸秆青贮的绵羊普雷沃氏菌相对丰度较高。经预处理的青贮在门水平上降低了瘤胃液厚壁菌门的相对丰度。饲粮添加LP或LB可提高瘤胃普雷沃氏菌属、瘤胃球菌属和纤维杆菌属的相对丰度。对比玉米秸秆组和玉米秸秆青贮组，共检出瘤胃差异代谢产物498种。LP、LB处理的青贮相比，未处理的青贮分别检测到257和141种差异代谢物。这些代谢产物在绵羊瘤胃中与细菌群落相关，尤其是丁利弧菌、纤维杆菌和普雷沃氏菌。综上所述，青贮期间添加乳酸菌接种剂可通过影响瘤胃细菌群落而改变瘤胃发酵和代谢产物。这些接种剂带来的变化可能有利于反刍动物的生产性能和健康。