Stable carbon and nitrogen isotopic fractionation between diet and swine tissues

Naturally occurring stable isotope ratios can be a powerful tool in studies of animal nutrition, provided that the assumptions required for dietary reconstruction are validated by studies such as the one presented here. The objective of this study was to document the magnitude of isotopic fractionation between swine diet and their different tissues. For this, the isotopic ratios of carbon and nitrogen of the diet and selected tissues (hair, nail, liver, muscle, fat and cartilage) were determined. The delta C-13 and delta N-15 of the diet were -15.9 parts per thousand and 1.3 parts per thousand, respectively, and all delta N-15 of swine tissues were 2.2 to 3.0 parts per thousand enriched in N-15 in relation to the diet. Little variation in delta N-15 occurred among tissues, with exception to liver that was less enriched in N-15 than the nail. Nail and hair presented no C-13 enrichment relative to diet. Cartilage was similar to 1.0 parts per thousand enriched in C-13 as compared to diet. Liver and muscle were on average 2.1 parts per thousand more depleted in C-13 in relation to diet as well as fat tissues. Some of the C and N isotope ratios of swine tissues differed in organs, but the isotopic fractionation trends among tissues appears to be similar to other mammals. Therefore our data provide a good baseline to interpret stable isotope patterns in domestic mammals (such as swine) in controlled or semi-controlled experiments.