Multi-Isotope Signatures in Modern Pig Bones: Evaluating Dietary and Hydrological Controls on Provenance in South Korea

Multi-isotope analysis of animal tissues is a powerful tool for provenance studies; however, its application to modern livestock is complicated by the widespread use of manufactured feed and managed water sources. In this study, we investigated the mechanisms by which dietary and hydrological isotope signals are incorporated into modern pig bone tissues and evaluated whether bone collagen (BC) and phosphate (BP) preserve interpretable provenance information. ⁸⁷Sr/⁸⁶Sr, δ¹³C, δ¹⁵N, and δ¹⁸O values were measured in pig bone, BC, and BP collected from 17 livestock farms across South Korea. Bone isotope compositions were compared with corresponding feed and groundwater values to assess the transfer of dietary and hydrological signals into skeletal tissues. Bone ⁸⁷Sr/⁸⁶Sr ratios ranged from 0.70991 to 0.72280 and largely overlapped with feed values (0.71009-0.71226), whereas groundwater values differed significantly from bone values (p < 0.0001), indicating that Sr incorporation was more strongly influenced by diet than by drinking water. However, the relative contributions of feed, groundwater and other sources were not quantified for source apportionment. δ¹³C_BC values ranged from -17.6‰ to -13.4‰, and δ¹⁵N_BC values ranged from 0.74‰ to 5.31‰. Both isotopic systems were significantly enriched relative to feed (p < 0.0001), with mean offsets of 1.69‰ and 1.72‰ for δ¹³C and δ¹⁵N, respectively. Both δ¹⁸O_BC and δ¹⁸O_BP were positively correlated with δ¹⁸O_Water, although BP exhibited relatively stronger explanatory power (R ² = 0.61) than BC (R ² = 0.40). These results suggest that modern pig bones retain measurable dietary and hydrological isotope signals; however, the use of manufactured feed can possibly weaken or obscure local geological provenance signatures. Notably this study provides a multi-isotope baseline for pig farms in South Korea and highlights both the potential and limitations of skeletal isotope analysis for provenance investigations of modern livestock systems.