Opportunistic pathogens, such as Phascolarctobacterium (significantly correlated with systemic inflammatory cytokines, such as TNF-α (Ling et al., 2016)), Campylobacter (ubiquitous in nature and in domestic animals, but also important in infections in animals) and Treponema_2 which belongs to phylum Spirochaetae and has been isolated from pig lesions (Svartstrom et al., 2013) were increased after antibiotic treatment compared to the NC group. This evidence concerns the gene TNF and infection.