Faecal cortisol metabolite (FCM) analysis is a reliable non-invasive method used in field endocrinology studies to assess levels of stress in animals. It is known that weather and, above all, humidity, can affect FCM concentrations in faecal samples. In addition, the prolonged storage of samples and delay in their analysis may alter metabolite concentrations. Intrinsic factors such as the heterogeneous distribution of FCMs within scats may likewise cause intra-sample variation. All of these sources of variation in FCM concentrations need to be addressed if we are to interpret results correctly. The aim of this study was to assess the effects of lyophilisation and storage temperature on the long-term stability of 11-oxoaetiocholanolone (11-o) in red deer (Cervus elaphus) faecal samples. After pre-cleaning with hexane and extraction with methanol, 11-o levels were analysed using high-performance liquid chromatography coupled with tandem mass spectrometry HPLC-MS/MS at 1, 2, 4, 6, 8, 16 and 32 weeks post-collection. We used linear mixed models to explore the effects of temperature and storage time on concentrations of faecal 11-o in wet and dry samples. Our results showed significant variations in 11-o concentrations in wet faecal samples over time and at different storage temperatures. By contrast, the 11-o values of dry samples were more stable in terms of storage temperatures. Lyophilising red deer faecal samples and storage at − 80 °C guarantees the stability of 11-o for several months.

中文翻译：

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不同储存条件下马鹿粪便样品中11-氧杂苯二酚的长期稳定性评估

粪便皮质醇代谢物（FCM）分析是一种可靠的非侵入性方法，用于野外内分泌学研究以评估动物的压力水平。众所周知，天气，尤其是湿度会影响粪便样品中的FCM浓度。此外，样品的长时间存储和分析的延迟可能会改变代谢物的浓度。内在因素（例如粪便中FCM的异质分布）可能同样导致样本内变化。如果我们要正确地解释结果，则必须解决FCM浓度变化的所有这些来源。这项研究的目的是评估冻干和贮藏温度对马鹿（鹿）中11-氧杂苯二酚（11-o）长期稳定性的影响。）粪便样本。在用己烷预清洗并用甲醇萃取后，使用高效液相色谱和串联质谱HPLC-MS / MS在1、2、4、6、8、16和32周后分析11-o的水平采集。我们使用线性混合模型来探索温度和储存时间对干湿样品中粪便11-o浓度的影响。我们的结果表明，在不同的储存温度下，随时间变化的湿粪便样品中11-o浓度存在显着变化。相反，干燥样品的11-o值在储存温度方面更稳定。将马鹿粪便样品冻干并在− 80°C下保存，可确保11-o保持几个月的稳定性。