Treatment by day interactions observed for mean coliform counts in the ceca. The in ovo inoculated treatments are represented as follows: Treatment 1, Marek's vaccine (MV) is denoted by the dark gray bar. Treatment 3, B. subtilis ATCC 8473, is denoted by the downward diagonal bar. Treatment 4, B. subtilis ATCC 9466 is denoted by the light gray bar. Treatment 2 did not yield enough birds to move to a grow-out facility and is not represented in the figure. Total bacterial counts in cfu/g are on the y-axis and the days of sampling during the grow-out are on the x-axis. Differences in mean bacterial count were considered significant at P ≤ 0.05. SEM = 0.473, P ≤ 0.0001, and N = 10 (10 cages/ treatment, 1 chick was randomly sampled from each cage on each sampling day). Significant differences are distinguished according to alphabetical superscripts, where means not sharing a common superscript are significantly different.