1. Assess the impact of dietary regimens, housing systems, and different chicken genetic lines on Salmonella (S.) infections of hens, Salmonella contamination of the production environment and eggs, and physical and functional egg quality. 1.a. Holistic comparison of genetic strains in commercial cage-free aviary housing. 1.b. Compare Salmonella shedding and microbial quality of eggs and environment in commercial-style conventional cage, enriched colony cage, enrichable colony cage, cage-free, and free range systems for various genetic strains of laying hens. 1.c. Assess the susceptibility of defined genetic lines of laying hens to infection with S. Enteritidis when housed in different cage-based production systems. 2. Assess the effects of key management practices using experimental and field models of different housing systems on hen health, microbial ecology of foodborne bacteria, and antimicrobial resistance associated with egg contamination. 2.a. Assess the effects of different stocking densities on S. Enteritidis infections in laying hens housed in enriched colony cages. 2.b. Assess the effects of different cage-based housing systems on infections of laying hens with Salmonella serotypes (other than Enteritidis) which are significantly associated with egg contamination. 2.c. Determine the impact of hen housing systems on prevalence, diversity, and antimicrobial resistance of Salmonella, Campylobacter, Listeria, and Enterobacteriaceae associated with the production environment and eggs.