LAUSR

The dynamics of the community structure and composition of the dairy cow fecal bacterial communities during early lactation is unclear, therefore this study was conducted to characterize the fecal bacterial communities in dairy cows during early lactation using 16S rRNA gene sequencing. Feces were sampled from 20 healthy fresh Holstein dairy cows on day 1 (Fresh1d group) and day 14 (Fresh14d group) after calving. After calving, cows were fed the same fresh diet. The dominant phyla Firmicutes and Proteobacteria were decreased ( P  ≤ 0.01) with lactating progress and phyla Bacteroidetes were increased ( P  = 0.008) with lactating progress and dietary transition. At family level, the predominant families were Ruminococcaceae (35.23%), Lachnospiraceae (11.46%), Rikenellaceae (10.44%) and Prevotellaceae (6.89%). A total of 14 genera were different between fecal samples from Fresh1d and Fresh14d, included the predominant genera, such as Ruminococcaceae_UCG - 005 ( P  = 0.008), Rikenellaceae_RC9_gut_group ( P  = 0.043) and Christensenellaceae_R - 7_group ( P  = 0.008). All fecal bacterial communities shared members of the genera Ruminococcaceae_UCG - 005 , Bacteroides and Rikenellaceae_RC9_gut_group . These findings help to improve our understanding of the composition and structure of the fecal microbial community in fresh cows and may provide insight into bacterial adaptation time and dietary in lactating cows.