Stable isotope analysis and variation in medieval domestic pig husbandry practices in northwest Europe: absence of evidence for a purely herbivorous diet

Results from other medieval sites in NW Europe show considerable variation in δ13C and δ15N values, indicating large variations in diet. However, none of the values are consistent with a diet wholly dominated by plant material; and therefore pig husbandry through outspan herding (pannage) without supplementary feeding. We question interpretations to the contrary, which neglect the role of known differences in dietary fractionation between species in producing δ13C and δ15N values of tissue. Data from domestic pigs of ancient breeds undoubtedly raised by outspan herding/pannage are so far unavailable and would be instructive.