Intra- and inter-individual variability of stable strontium isotope ratios in hard and soft body tissues of pigs.

Rationale Stable isotope analysis has become an indispensable tool for the identification of the flow of matter in ecological sciences. Stable strontium isotope ratios are used in several different scientific fields as markers for provenance, mobility, and migration. A crucial prerequisite for such studies is a reliable definition of local ranges and an estimation of expected isotopic variability. Methods To study the local variability of stable strontium isotope ratios at a specific place, a farrow of ecologically and locally grown pigs was investigated and strontium was extracted from their hard tissues (tooth enamel, bones and bristles) as well as soft tissues (meat, organs and blood) via dry- and wet-ashing procedures and subsequent column separation. The Sr-87/Sr-86 ratio was then measured via TIMS (thermal ionization mass spectrometry). Results Reliable Sr-87/Sr-86 data was generated from all tissue types. Both intra- and inter-individual variability was high and tissue-specific patterns could be identified. High ranges occurred in sample types which were analyzed for animals of different age (pigs as well as piglets): teeth, parietal, mandible, femur, and leg muscle as well as in jaw muscle samples, which were only analyzed in adult pigs. Tooth enamel data showed a tooth-type-dependent pattern. Conclusions We conclude that a time factor played a role for the observed variability, e.g. a shift in food supply. Furthermore, we presume that local range estimates from the literature only work for tissues which integrate all consumed components over a sufficient amount of time and average fluctuations which can be found in tissues with higher turnover rates.