Intrinsic labeling of chicken products with a stable isotope of selenium (76Se).

Chicken tissues were intrinsically labeled with a stable isotope of selenium (76Se) and were evaluated for use in a human feeding study. Laying hens were fed a low Se (0.06 ppm) basal diet for 39 days and then fed the basal diet supplemented with 0.3 ppm enriched 76Se (as selenite) for 35 days. Incorporation of 76Se into samples was determined by use of a double isotope dilution technique and a combined gas chromatography/mass spectrometry analysis. The 76Se content of the basal diet was increased by a factor of 9.7 with the addition of the enriched stable isotope. This maximal level of enrichment was approached in egg yolk (9.5-fold) and liver (9.0-fold). Enrichment was lower in egg white (7.2-fold) and breast meat (5.0-fold). Level of enrichment in a given tissue reflected both the turnover rate of the tissue and its natural selenium content. Selenium-depleted laying hens continuously fed 76Se at the 0.3 ppm level produced egg yolks and livers that were enriched sufficiently with the stable isotope for use in a human metabolic study.