To evaluate myoblast proliferation activity, cells were subjected to thymidine-incorporation assay (Figure 4). Thymidine incorporation was significantly higher in the myoblasts of the TM embryos compared to controls until E13 (for 24H treatment) or E15 (for 12H treatment) (Figure 4a). Afterward, myoblasts derived from TM embryos exhibited significantly lower proliferation activity until hatch. During the first week posthatch, myoblast proliferation activity was significantly higher in both TM groups compared to controls. However, at 2 wk of age it was significantly lower (Figure 4b).