Exploring the Effects of Transport Duration on the Fecal Microbial Communities of Surplus Dairy Calves.

Transportation significantly impacts the health and welfare of surplus dairy calves largely due to the various stressors and pathogen exposures encountered during the process. Concurrently, the animal's microbiome is known to correlate with its health status, with stress-induced alterations in the microbiota potentially precipitating various diseases. This study aimed to compare the impacts of transportation durations of 6, 12, or 16 h on the fecal microbiota in young surplus dairy calves. We used a randomized controlled design, where surplus dairy calves aged 1–19 d old from 5 commercial dairy farms in Ontario were allocated into one of 3 (6, 12, and 16 h of continuous transportation) transportation groups. Health assessments were conducted before, immediately after, and for 2 weeks following transportation. Fecal samples were collected before, immediately after, and at 24- and 72 h post-transportation and subjected to 16S rRNA sequencing. Alpha diversity metrics showed no significant differences between the 3 transportation groups at any of the sampling time points. Although β diversity metrics revealed no clustering by transportation groups, they indicated significant differences across sampling time points within each group. The overall analysis revealed a total of 22 phyla and 353 genera, with Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, and Fusobacteria being the most abundant phyla. Bacteroides, Escherichia/Shigella, Lactobacillus, Collinsella, and Bifidobacterium were the most abundant genera. The reduction in Fusobacteria abundance before and after transport was significantly larger in the 16-h transportation group when compared with the 6-h transportation group. We also identified several genus-level and ASV-level taxa that displayed significant differences in their abundances across various transportation groups, observed at all sampling time points investigated. In conclusion, this research identifies microbiota changes due to varying transportation durations in surplus dairy calves providing a broad understanding of the microbial shifts in surplus dairy calves' post-transportation across varying durations. While these variations may not directly correlate with overall calf health or indicate dysbiosis, these results emphasize the importance of further investigating transportation practices to enhance calf health and well-being. Further studies are warranted to elucidate the relationship between microbiota and calf health.