Steady-state erythropoiesis in the C57BL/6 mouse bone marrow is established within 7 weeks after birth. (A) Terminal erythroid differentiation in the bone marrow for the first 12 weeks after birth was measured by flow cytometry using CD44 vs FSC as markers. (B) The total number of erythroblasts in the bone marrow for the first 12 weeks was determined by flow cytometry using Ter119⁺ CD44^hi populations of erythroid cells (red gate is shown in panel A). (C) Absolute number of bone marrow cells for the first 12 weeks. (D) Evolution of the mouse body weight (blue solid lines) vs bone marrow weight (red solid line) from week 1 to week 12. n = 4-13 animals per day using 1 femur and 1 tibia for each animal; data are presented as mean ± SEM. *P < .05, **P < .01, ***P < .001, ****P < .0001, indicated week vs week 1 (ANOVA with Tukey’s post hoc test with corrections for multiple comparisons).