Neonatal Calf Diarrhea Is Associated with Decreased Bacterial Diversity and Altered Gut Microbiome Profiles

Neonatal calf diarrhea (NCD) is a broad symptom encompassing many potential underlying causes. While alterations in the gut microbiota have been correlated with diarrhea, the effects of diarrhea on gut communities have not been sufficiently studied. To explore these effects and identify key microbiota involved, we profiled the fecal microbial community of 21 calves with varying health conditions using the 16S rRNA gene. In comparison to healthy calves, diarrheic calves exhibited significantly decreased diversity and evenness indices. There was a notable increase in the relative abundance of Proteobacteria and Actinobacteriota, and a significant decrease in the relative abundance of Bacteroidetes. At the genus level, there were increased relative abundances of Escherichia-Shigella and Lactobacillus. Notably, the abundance of Lactobacillus continued to increase during the recovery from diarrhea. Clinical observation and bacterial typing analysis revealed fecal microbiome dysbiosis as a significant characteristic of NCD. This work identifies dysbiosis as a key factor promoting diarrhea in neonatal calves, characterized by a low-diversity microbiome. The increased abundance of Lactobacillus might contribute to the curative properties of diarrhea.