不同分级指数燕麦干草对奶牛体外发酵营养物质降解率、瘤胃发酵参数和微生物组成的影响

Effects of different grading index oat hay on nutrient degradation rate,rumen fermentation parameters and microbial composition of dairy cows fermented in vitro

本试验采用体外发酵法评价不同粗饲料分级指数(GI)燕麦干草的饲用价值,为其在奶牛生产应用中提供理论依据。选取3种不同GI的燕麦干草分为3组,试验1组、试验2组和试验3组GI值分别为4.26、10.98、11.60MJ/d,体外发酵24 h。结果表明:(1)试验2组和试验3组干物质、粗蛋白质和中性洗涤纤维降解率显著高于试验1组(P<0.01),其中干物质降解率比试验1组分别高50.95%、55.37%;中性洗涤纤维降解率分别高54.41%、50.47%。(2)试验2组和试验3组氨态氮、乙酸、丙酸、丁酸、戊酸和TVFA高于试验1组(P<0.05),其中TVFA比试验1组分别高13.39%和11.05%。(3)各组优势菌门由拟杆菌门(Bacteroidota)和厚壁菌门(Firmicutes)组成,两者占整个菌群89%以上,其中厚壁菌门相对丰度具有差异显著趋势(P=0.07);各组优势菌属组成相同,各组中未分类理研菌科(Unclassified_f_Rikenellaceae)、未知属-绒毛杆菌科(Norank_f_Muribaculaceae)、纤维杆菌属(Fibrobacter)具有显著性差异(P<0.05),其中试验2组和试验3组纤维杆菌属比试验1组分别低51.36%和55.45%。综合结果,不同GI等级燕麦干草对奶牛营养物质降解率和瘤胃发酵特性具有明显影响,且GI等级越高,其营养价值就越好。

In this experiment,the in vitro fermentation method was used to evaluate the feeding value of different forage grading index(GI)oat hay,and to provide a theoretical basis for its application in dairy cattle production.Three kinds of oat hay with different GI were selected and divided into 3 groups.The GI values of text group 1,text group 2 and text group 3 were 4.26,10.98,11.60 MJ/d,respectively.Fermentation in vitro for24 hours.The results showed as follows:(1)The dry matter degradation rate,crude protein degradation rate and neutral detergent fiber degradation rate of test group 2 and test group 3 were significantly higher than those of test group 1(P<0.01).Among them,the dry matter degradation rate of test group 2 and test group 3was 50.95%and 55.37%higher than that of test group 1,respectively.(2)The NH3-N,acetic acid,propionic acid,butyric acid,valeric acid and TVFA in test group 2 and test group 3 were higher than those of test group1(P<0.05).Among them,the TVFA of test group 2 and test group 3 were 13.39%and 11.05%higher than that of test group 1,respectively.(3)The dominant phyla in each group composed of Bacteroidota and Firmicutes,which accounted for more than 89%of the entire flora,and the relative abundance of Firmicutes has a significant trend of difference(P=0.07).The composition of dominant bacterial genera in each group was the same,and there were significant differences in Unclassified_f_Rikenellaceae,Norank_f_Muribaculaceae and Fibrobacter in each group(P<0.05).Among them,the Fibrobacter of test group 2 and test group 3 were51.36%and 55.45%lower than that of test group 1,respectively.The comprehensive results showed that different GI grades of oat hay had significant differences in the nutrient degradation rate and rumen fermentation characteristics of dairy cows,and the higher the GI grade,the better the nutritional value.