Intra-bone variability of collagen and apatite isotopic composition used as evidence of a change of diet

A study of intra-individual variability of the isotopic composition of mineralized tissues was conducted on five modern steers (Bos taurus) whose diet shifted in the middle of their life time from a C3 milk-based diet to a C4/C3-herbivorous diet. This dietary change was reflected in δ15N and δ13C values of collagen and carbonate hydroxylapatite from both tooth and bone. Material from the top and the bottom of the second lower molar gave isotopic signals of collagen and apatite synthesized exclusively before and after the change of diet. In the jawbone, the change of diet was reflected in a difference of isotopic composition of material sampled in the first molar socket zone (M1-bone) on the one hand, and in the dental bud socket zone (db-bone) on the other. M1-bone and db-bone were both found to be made of a mixture of ante- and post-dietary change material. However, the amount of newly synthesized material was clearly higher in db-bone, which was expected because of the remodelling of this part of the jawbone, to allow dental eruption.