Abstract:

[Objective] This study was conducted to assess the effects of dietary supplementation of compound ethanol extracts from Taraxacum mongolicum, Leonurus japonicus, Lonicera japonica and Forsythia suspensa on rumen bacterial flora in lactating Holstein dairy cows. [Method] A total of 24 lactating Holstein dairy cows were randomly allocated to a control group （n=12） or an experimental group （n=12） by using a completely randomized experiment design. The control group fed a basal diet, and the experimental group fed the same basal diet supplemented with 0.3% compound plant extracts of DM per cow per day. The experiment lasted for 75 days, including a 15-day pre-experiment and a 60-day formal experiment. On day 60 of the formal experiment, the rumen fluid samples were orally collected and the total DNA was extracted. The impacts of dietary supplementation of compound plant extracts on variation of rumen bacterial flora in dairy cows were evaluated by using 16S rDNA sequence analysis. [Result] The rumen microorganisms in the experimental group and the control group could be separated from each other at the OTU level. The α diversity index of rumen bacteria in the experimental group was not significantly （P>0.05） different from that in the control group. Dietary supplementation of compound plant extracts altered the relative abundance of 17 bacterial phyla in rumen in dairy cows to a certain extent, but no significant （P>0.05） differences were observed. At phylum level, Bacteroidetes and Firmicutes accounted for the highest proportions in total rumen bacteria. At genus level, the relative abundance of rumen bacteria in the experimental group was not significantly （P>0.05） different from that in the control group, and the dominant bacteria were Prevotella 1 in both of the groups. Linear discriminant analysis effect size （LEfSe） demonstrated that compared with the control group, the relative abundance of Bacteroidales in the experimental group was significantly （P<0.05） reduced, and that of Bifidobacteriaceae was significantly （P<0.05） elevated. [Conclusion] Dietary supplementation of 0.3% compound extracts from Taraxacum mongolicum, Leonurus japonicus, Lonicera japonica and Forsythia suspensa has regulatory effects on rumen bacterial flora in lactating Holstein dairy cows.

Key words: Taraxacum mongolicum, Leonurus japonicus, Lonicera japonica, Forsythia suspensa, compound plant extracts, dairy cows, rumen bacterial flora