Abstract

In order to use faecal samples as means of laboratory diagnostics to analyze the mineral supply of organisms, it is necessary to define standardized sampling requirements. The present investigations monitor the variation of concentrations of mineral compounds within faeces as well as influences, such as age and storage of the samplings.

The faecal sample was separated horse dung of a female German Warmblood horse, which was appropriately provided with minerals according to supply recommendations. It was examined within nine different localizations, immediately after defecation, as well as 24 and 72 hours later. Moreover, six additional samplings of other horses were portioned into four different containers and stored for seven days at -18°C, -8°C, 8°C and 20°C. Afterwards, the samplings were dried and examined. With the help of ICP-OES and ICP-MS and due to standardized instructions 28 elements were identified. Furthermore, the relative error of the method was calculated.

Within the faeces, the concentration of identified elements is increasing from inner to outer regions. Considering the horizontal and vertical variation, the former showed significant differences between three, the latter one between eleven elements. The laps of time between defecation and sample taking significantly affected the concentration of mineral compounds in 16 cases, although the samplings do not vary until 24 hours after defecation. In contrast to that, there was an increase in the concentration of mineral compounds 72 hours after sample taking. The storage does not significantly influence the concentration of mineral compounds of the faeces, except from two elements.

The increase in mineral compounds together with rising sampling age and further distance to the centre of the heap is due to the relative rise, after volatile compounds decreased. The storage does not have an effect on the traceable concentration and thus, the two divergent elements are attributed to random variation. Moreover, the existing stability of concentrations in faecal samples does have a clinical relevance and, accordingly, a standardised procedure should consider sample taking of more central localizations of currently excreted dung. Additionally, in case of long-lasting storage, the samples should be kept chilled. The only exception to diverge from this procedure is the analysis of samples taken from the center of the dung within three days after defecation.

Keywords: Storage; Age of Samples; Variation; Analysis of Mineral Compounds; Horse; Faeces

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