Study On The Changes Of Rumen Bacterial Flora In Dairy Cows Under The Model By Inducting With Low Milk Fat Diet

Four Chinese Holstein dairy cows with similar body weight and parity were selected in the same pen.A completely randomized design test scheme was adopted.Pre-feeding with basal diet was used as control group（CK）for 7 days.Starting from the formal period of the experiment,milk fat of dairy cows was reduced by feeding crushed corn on the basis of basal diet,which was used as group I（C）for 15 days.After the end of experiment I,milk fat of dairy cows continued to decrease（CO）by feeding crushed corn and oil on the basis of basic diet.As experiment II group,the experiment period was 15 days.The purpose of this study was to study the changes of rumen microflora under these two typical low-fat diets,and to provide theoretical basis for further study on the mechanism of milk fat decline in dairy cows,as well as to provide guidance for dietary regulation.The results are as follows:（1）Under the induction of two different low-fat diets,the milk fat rate was significantly reduced（P<0.01）,and the lowest was found in CO group,and the lactose content was significantly increased after adding linseed oil and fine corn（P<0.05）.（2）Under fine-corn-induced low-milk-fat mode,the bacteria that changed significantly in the rumen of dairy cows involved 6 phylums and 90 genera,which significantly promoted the proliferation of acid-producing bacteria.The dominant bacteria were Acetobacter,Lactobacillus,Pediococcus,Leuconostoc,Lachnotridium-1,Ruminococcus₁,Pseudoscardovia and Lactococcus increased significantly（P<0.05）.（3）Under the low-milk-fat mode induced by fine corn and oil mixture,the bacteria that changed significantly in rumen of dairy cows involved 4 phylums,110 genera,and significantly promoted the proliferation of acid-producing bacteria.The dominant bacteria were Lactobacillus,Leuconostoc,Acetobacter and Roseburia（P<0.05）.The growth of most rumen fiber-degrading bacteria was significantly inhibited,most acid-producing bacteria were significantly increased,and some lactic Acid-utilizing bacteria were significantly inhibited.（4）Compared with fine corn and fine corn oil combination,rumen bacteria of dairy cows reached a significant difference level in 5 phylums and 68 genera,of which the dominant bacteria were Westerella,Ruminococcaceae_UCG-010,Acetobacter,Selenomonas₁,Mitsuokella,Leptotrichia,Veillonellaceae_UCG-001 and Vibrio in group C was significantly higher than that in group CO（P<0.05）.