Measurement of glucocorticoid metabolite concentrations in faeces of domestic livestock

After C-14-labelled cortisol infusion in ponies and pigs, faecal samples we re collected. Extraction of 0.5 g faeces with 5 ml 80-90 % methanal yielded the highest radioactivity in the supernatant. Most of the metabolites were ether soluble. After high performance liquid chromatography (HPLC), the pr esence of immunoreactive metabolites was demonstrated bp measuring each HPL C fraction using enzyme immunoassays for cortisol, corticosterone and 11-ox oaetiocholanolone. Only the assay for 11-oxoaetiocholanolone revealed peaks with co-eluting radioactivity. For biological validation of the test syste m, adrenocorticotrophic hormone (ACTH) and dexamethasone were injected intr avenously successively in both species (n = 6). Cortisol concentration in b rood and the 11-oxoaetiocholanolone immunoreactive substances in faeces wer e determined. In horse faeces, basal values of 2.3-35.2 nmol/kg were measur ed. After ACTH administration, an increase (more than 200 % above basal val ues) of these metabolites nas seen about 1 day after ACTH administration. A fter dexamethasone injection the levels decreased, reaching minimum concent rations 2 days after administration. In pigs, an increase in these metaboli tes was measured in only three animals after ACTH; dexamethasone did not ca use a decrease. The stability of the samples after defecation was tested by storing samples from cows, horses and pigs at room temperature. It was sho wn that there was a significant increase in the concentration of measured c ortisol metabolites in bovine, equine and porcine faeces after storage for 1 h, 4h and 24 h, respectively. In frozen samples this effect was diminishe d after thawing samples at 40 degrees C; thawing the samples at 95 degrees C prevented an increase in immunoreactive substances.