Body weight and sternal characters of 49-day-old meat duck responses to 25-OH-D3 in PC diet with NRC vitamin regimen. (A) Body weight, (B) Sternum relative weight (per 100 g body weight), (C) fat-free weight, (D) sternum length, (E) depth, (F) coracoid distance, (G) sternum central distance, and (H) posterior process distance. Values are means and standard deviation represented by vertical bars (n = 8). a, bMean values with different letters are significantly different (one-way ANOVA, P < 0.05, Tukey's post hoc test). Abbreviations: 25-OH-D3, 25-hydroxycholecalciferol; PC, positive control.