Mechanical brushing, social interaction and gut microbiota analysis: Gut-brain axis directed gut microbiota in healthy calves before and after mechanical brushing

Özet

Mechanical brushes are well-recognized grooming tools widely adopted to improve the well-being of dairy cows and calves, and automated brushing has been reported to interact with social networks and behaviour in several species. Building on these observations, the present study hypothesized that calves that naturally investigate and use mechanical brushes may undergo shifts in gut microbiota composition, potentially mediated by social interaction and the associated skin–oral network. This field study was conducted under commercial farm conditions in apparently healthy calves aged 30–70 days that were socially bonded to their pen mates and used a mechanical brush at least daily. Infectious enteropathogens were excluded using point-of-care rapid diagnostic test kits. Faecal samples were collected rectally before brushing and after three weeks of mechanical brush use. Following extraction of faecal DNA, the V4 and V4–V7 regions of the 16S rRNA gene were amplified and sequenced on the Illumina iSeq100 platform (2 × 150 bp), and data were processed using QIIME 2 and Kraken2 with taxonomic assignment against the SILVA database. Before brushing, the microbial community was dominated by Yersinia enterocolitica (25.9%), others (26.7%) and Pseudomonas tolaasii (9.94%). After three weeks, the relative abundances of Y. enterocolitica and P. tolaasii fell to 10.1% and 5.75%, respectively, while taxa absent at baseline — Haloquadratum walsbyi (14.9%), Methanobrevibacter smithii (13.0%) and Bacteroides uniformis (5.50%) — became established. Increased proportions of Phocaeicola vulgatus, [Ruminococcus] torques and Pedobacter sp. HDW13 were also recorded, whereas Burkholderia pyrrocinia, Defluviimonas sp. SAOS 178_SWC and Streptomyces sp. NBC_00536 were no longer detected. The reduction in potential pathogens, most notably Y. enterocolitica, is of particular interest given its role in enteric disease of cattle and its zoonotic importance. To the best of the author’s knowledge, this is the first report associating mechanical brushing with gut microbiota alterations in calves, providing a rationale for enrichment-based interventions targeting gut health and welfare.