This study investigated the efficacy of feed additives as alternatives to antibiotics in controlling post-weaning *Streptococcus suis* disease in swine. Five groups of piglets were fed diets supplemented with lysozyme, medium-chain fatty acids (FA) plus lysozyme, FA plus a natural anti-inflammatory, amoxicillin, or a control diet. The FA plus anti-inflammatory and amoxicillin groups showed lower prevalence of *S. suis*-like clinical signs. The FA plus anti-inflammatory group exhibited higher nasal and faecal microbiota diversity. Nasal microbiota showed more significant changes than faecal microbiota, and dam parity influenced offspring microbiota composition. The findings suggest that feed additives can help control post-weaning disease while reducing antibiotic use.

Florencia Correa-Fiz, Carlos Neila-Ibáñez, Sergio López-Soria, Sebastian Napp, Blanca Martinez, Laia Sobrevia, Simon Tibble, Virginia Aragon, Lourdes Migura-Garcia