Bone phenotypes responses to 25-OH-D3 and vitamin regimen in LND diet for meat duck at 49 D. (A) Toluidine blue stained and the morphometric analysis for (B) trabecular bone volume/tissue volume (BV/TV), (C) trabecular thickness (Tb.Th), (D) number (Tb.N), and (E) spacing (Tb.Sp). Real-time RT-PCR analysis of osteocyte markers gene including (F) Phosphate regulating endopeptidase homolog x-linked (Phex), (G) Sclerostin, and (H) Dentin matrix protein1 (Dmp1) in the sternum. Values are means and standard deviation represented by vertical bars (n = 8). a–cMean values with different letters are significantly different (two-way ANOVA, P < 0.05, Tukey's post hoc test). Abbreviations: 25-OH-D, 25-hydroxycholecalciferol; NY/T, China Agricultural industry standards; LND, low nutrient density.