Carbon isotope fractionation between diet, breath CO2, and bioapatite in different mammals

The carbon isotope fractionation between tooth enamel bioapatite, breath CO2, and diet was measured for voles, rabbits, pigs, and cattle on controlled diets. The measured fractionation (expressed as isotope enrichment ɛ*) between enamel and diet was 11.5 ± 0.3‰, 12.8 ± 0.7‰, 13.3 ± 0.3‰, and 14.6 ± 0.3‰ for these respective species. There is a 1:1 correlation between ɛ*breath-diet and ɛ*enamel-diet (r2 = 0.94, p < 0.01), whereas our data do not resolve significant inter-species differences in ɛ*enamel-breath. These findings are consistent with the hypothesis that inter-species differences in ɛ*bioapatite-diet are primarily a result of differences in digestive physiology, rather than differences in the magnitude of fractionation between mineral and body fluid.