Neonatal calf diarrhea is associated with decreased bacterial diversity and altered gut microbiome profiles

Neonatal calf diarrhea (NCD) is a broad symptom and has many potential underlying causes. Alterations in the gut microbiota are correlated with diarrhea, however, the effect of diarrhea on gut communities has not been sufficient studied. To explore the effect of diarrhea on the gut microbiota in neonatal calves and determine key microbes contributed to diarrhea development, impact, and recovery, we profiled fecal microbial community composition using the 16S rRNA gene in 21 calves that presented with health or diarrhea. Compared with healthy calves, the indices of diversity and evenness of diarrheic calves were significant decreased, whiling, the relative abundance of Proteobacteria and Actinobacteriota were significant increased; the relative abundance of Bacteroidetes was significant decreased; At the genus level, the relative abundance of Escherichia-Shigella and Lactobacillus increased. The abundance of Lactobacillus continued to increase during the recovery of diarrhea. Through clinical observation and bacterial typing analysis, dysbiosis of fecal microbiome is one of the major characteristics of NCD. This work identifies diarrhea is associated with a low-diversity microbiome, dysbiosis as one key factor promoting diarrhea in neonatal calf. The increased abundance of Lactobacillus might contribute to diarrheic curative properties.