Colonization of R. anatipestifer CH-1 and its fur mutant in ducklings at 24 h and 48 h post-infection. Doses (200 μL) of 109 CFU of R. anatipestifer CH-1pLMF03, R. anatipestifer CH-1ΔfurpLMF03 and R. anatipestifer CH-1 ΔfurpLMF03::fur were prepared and injected intramuscularly into 3-day-old ducklings (20 ducklings/group). At 24 h (A) and 48 h (B) post-infection, bacteria were isolated from the livers, spleens, brains, and the blood from the heart, as described in the “Materials and methods”. The data points represent the CFU/g values of the indicated organs in individual ducklings; the bars show the mean values (n = 6). Statistical significance was determined using two-way ANOVA (****P < 0.0001, ** P < 0.01).