Development of gut microbiota composition in captive Asian elephants: a year-long analysis

The establishment of gut microbiota is vital for the health and development of elephant calves, especially during their first year of life. This study investigates the transformation of the gut microbiome in captive Asian elephant calves, focusing the influence of maternal milk and subsequent dietary transitions on microbial colonization. A single meconium was collected at birth, followed by monthly fresh fecal samples during the first year. Mothers' fecal samples were also collected when calves reached three months of age. Gut microbiota profiling was conducted using 16 S rRNA gene sequencing. Meconium exhibited a diverse microbiota with moderate richness at birth. Richness subsequently declined in the monthly fecal samples, reaching its lowest point by three months of age. Firmicutes, Actinobacteriota, and Bacteroidota were the dominant bacterial phyla throughout the first year. A major shift was observed around 7 to 8 months of age with emergence of the archaeal genus Methanobrevibacter from phylum Euryarchaeota, which subsequently declined by 11 to 12 months. By this age, the calf microbial community had become more similar to that of adult elephants; however, species richness and diversity remained lower, indicating that microbial maturation was still ongoing. These findings advance our understanding of gut microbiota development in elephant calves and underscore the critical role of dietary management in promoting gut health and survival, providing essential data for captive conservation and management strategies.