The problem of quality and comparability of chimpanzee faecal samples before hormonal analysis: Variability and standardisation
Abstract
Due to the dissimilar nature of analysed faecal material (soaked vs. dried samples) used in different studies it may be difficult to obtain comparable results. In the initial part of the study, we analysed 70 fresh faecal samples collected in the morning from 6 mature male and female common chimpanzees at the Liberec Zoo (Czech Republic).
After deeply frozen samples were thawed, they were extracted by a non-aqueous solvent. After vortexing and centrifugation, supernatants were transferred into new vials, evaporated and the residue was redissolved with phosphate-buffered saline.
Aliquots were analysed for concentrations of testosterone and cortisol with competitive enzyme-immunoassays. Firstly, the extraction procedure was sufficient for testosterone EIA sensitivity; however, the absorbance values for cortisol were at the limit of detection or undetectable in about 95% of the samples tested.
Secondly, the samples were markedly variable in content of water and the amount of undigested particles.