Performance of several Cr and Yb analytical techniques applied to samples of different biological origin (digesta or faeces)

This paper compares the performance, in terms of Cr (liquid phase marker) and Yb (solid phase marker) recovery from spiked samples, of five mineralization procedures applied to faeces, whole duodenal digesta, particulate and liquid phases of duodenal digesta, whole ruminal digesta and ruminal fluid from cattle. Two Holstein-Friesian heifers, fitted with permanent ruminal and duodenal cannulae, and fed twice daily on barley straw and a concentrate (15:85), were used as sample donors. Cr and Yb were added to the samples at 5, 25, 125 and 625 (mu)g g^-1 dry matter, and analyzed by atomic absorption spectrometry. There were differences in marker recovery (p = 0.0481) depending on the mineralization procedure utilized but their performance was not affected by marker type (p = 0.6143). The interaction between type of sample and digestion procedure was statistically significant (p = 0.0290) and the results showed that homogeneous samples (whole duodenal digesta, the particulate phase of duodenal digesta and faeces) allowed the more even distribution of the marker and an easier and more complete mineralization. In contrast, heterogeneous samples (whole rumen digesta and rumen fluid) resulted in either a lesser attachment of markers to the particles and/or incomplete mineralization of the samples, which resulted in a higher variability between procedures. The interaction between type of sample and marker was also significant (p = 0.0426), with Cr recovery being more affected by type of sample than Yb.