Non-typhoidal Salmonella (NTS) cause salmonellosis in dairy cows, resulting in diarrhea, abortion, endotoxemia, and decreased milk production. The emergence of multi-drug resistant Salmonella has contributed to morbidity and mortality in humans and cattle. Innovative strategies to combat NTS on dairy farms, while preserving the efficacy of medically important antibiotics, is a high research priority. Salmonella enterica Serotype Cerro (S Cerro) is an emerging serotype on dairy farms in Wisconsin and nationwide and is thought to be less severe. This team hypothesizes that initial S Cerro colonization can prevent disease from virulent NTS in a process called competitive exclusion. To test this, calves colonized by S Cerro will be infected with virulent NTS to determine if S Cerro is capable of competitive exclusion. The goal of this project is to evaluate S Cerro as a potential therapeutic by determining its impact on the host immune response and on microbiota development. This project aligns to Dairy Task Force 2.0 recommendation #9 (‘Support the National Dairy FARM Program or equivalent’).