Temporal changes in the fecal microbiome and blood metabolites of early neonatal calves

Abstract

The initial colonization and early development of the intestinal microbiome are important stages in the growth of calves during pre-weaning. This study investigated temporal changes in the diversity and composition of the fecal microbiota, focusing on the first 2 weeks after birth, with the aim of identifying intestinal bacteria and blood metabolites that are associated with calf diarrhea. In this study, 10 calves were fed colostrum on day 0 after birth, whole milk from days 2 to 5, and milk replacer from day 6. Six calves showed mild diarrhea in the second week (i.e., from day 8 to 14). We observed dramatic changes in the development of the fecal microbiome from day 2 to 14 and found several bacterial species, such as Lactobacillus and Collinsella, changing significantly in abundance during the milk transition (i.e., from day 4 to 10). In investigating whether there is an association between the microbiome and the milk transition, we found the level of hypotaurine and D-xylose to be significantly higher in whole milk from days 4 and 5 than in milk replacer. A comparison of four healthy calves and six diarrheal calves revealed that the diarrheal calves had a low abundance of Collinsella on day 10. Furthermore, we explored plasma metabolites statistically correlated with the change of fecal Collinsella and found a high level of dimethylglycine in healthy calves. Taken together, these findings suggest a possible link between temporary changes in the fecal microbiome and neonatal diarrhea during the milk transition in calves.