Updated project metadata. Pioneer colonization of the gastrointestinal tract by bacteria is thought to have major influence on neonatal tissue development. Previous studies have shown in ovo inoculation of embryos with saline (S), species of Citrobacter (C, C2), or lactic-acid bacteria (LAB) resulted in an altered microbiome on day of hatch (DOH) and by 10 days of age. The current study investigated GIT proteomic changes in relation to different inoculations at DOH and by 10 days of age.