Stable carbon and nitrogen isotope analysis as a tool for inferring beef cattle feeding systems in Japan

A pilot study was conducted to evaluate the suitability of stable isotope analysis for inferring the feeding histories of cattle fed known feeds. Stable isotope ratios of carbon and nitrogen (δ13C and δ15N) were measured in meat and hair from cattle and in their feeds at five farms in different regions of Japan, and the correlations of the isotope ratios between meat and hair were analysed. The results showed that δ13C values in feed depend on the photosynthesis type: C3 or C4. The values of δ15N in feeds varied widely, indicating divergent feeds made from plant materials that have different nitrogen origins, such as soil, chemical fertilizer, manure and air. In both cattle meat and hair, the farms differed significantly in the values of δ13C and δ15N. Both δ13C and δ15N were significantly higher in hair than in meat, and high correlations between meat and hair in both δ13C and δ15N were found. The results suggested that stable carbon and nitrogen isotope analysis for cattle meat and hair could be used to trace the feeding histories of cattle in Japan, and that hair samples would be used as an alternative to meat.