Millspaugh Joshua J, Washburn Brian E
Department of Fisheries and Wildlife Sciences, University of Missouri, 302 Anheuser-Busch Natural Resources Building, Columbia, Missouri 65211, USA.
Gen Comp Endocrinol. 2003 Jun 1;132(1):21-6. doi: 10.1016/s0016-6480(03)00061-3.
Fecal glucocorticoid metabolite analysis is a useful tool for monitoring adrenocortical activity in captive and free-ranging wildlife. Glucocorticoid metabolites may not be evenly distributed within fecal samples and this variability could affect the interpretation of glucocorticoid metabolite measurements. Furthermore, the precision (i.e., repeatability of measurements) of fecal glucocorticoid measurements from well-mixed samples is unknown. We collected fresh white-tailed deer (Odocoileus virginianus) feces at various times pre- and post-adrenocorticotropin injection to provide samples with low (<75 ng/g), medium (75-90 ng/g), and high (>90 ng/g) glucocorticoid concentrations in case variability differs in samples of dissimilar hormone metabolite concentrations. We compared two sampling methods (selection of three pellet groups [one from each end of the fecal mass and one from the center] versus sampling three small portions of the thoroughly mixed fecal mass) to estimate within-sample variation of glucocorticoid metabolites. Glucocorticoid metabolite measures from pellet groups were higher than fecal glucocorticoid measures from mixed samples in the low (F=3.10; df = 1,56; P=0.08) and medium concentration (F=7.28; df = 1,50; P=0.01) groups. Fecal glucocorticoid metabolite estimates from mixed samples were less variable than glucocorticoid metabolite measures using pellet groups from the same fecal mass, although these differences were not statistically significant (low group: F=0.59; df = 1,38; P=0.45; medium group: F=0.13; df = 1,34; P=0.72; high group: F=2.30; df = 1,28; P=0.14). The mean coefficient of variation was <10% across all treatment groups and sampling methods. However, a power analysis indicated the mixed sub-sample technique requires fewer samples to detect statistically significant differences than pellet groups. Our results suggest that glucocorticoid metabolites may not be evenly distributed in white-tailed deer feces. Consequently, using only a few pellets from a fecal mass may bias assay interpretation. We suggest researchers homogenize the entire fecal mass before removing a sub-sample of fecal material for analysis. Also, other sources of variation must be considered when interpreting results of fecal glucocorticoid studies.
粪便糖皮质激素代谢物分析是监测圈养和自由放养野生动物肾上腺皮质活动的一种有用工具。糖皮质激素代谢物在粪便样本中可能分布不均，这种变异性可能会影响对糖皮质激素代谢物测量结果的解读。此外，来自充分混合样本的粪便糖皮质激素测量的精密度（即测量的可重复性）尚不清楚。我们在注射促肾上腺皮质激素前后的不同时间收集新鲜的白尾鹿（弗吉尼亚鹿）粪便，以提供低（<75 ng/g）、中（75 - 90 ng/g）和高（>90 ng/g）糖皮质激素浓度的样本，以防不同激素代谢物浓度的样本变异性有所不同。我们比较了两种采样方法（选择三个粪粒组[一个来自粪便团块的一端，一个来自中间，一个来自另一端]与从充分混合的粪便团块中采样三个小部分），以估计糖皮质激素代谢物的样本内变异性。在低浓度组（F = 3.10；自由度 = 1,56；P = 0.08）和中浓度组（F = 7.28；自由度 = 1,50；P = 0.01）中，粪粒组的糖皮质激素代谢物测量值高于混合样本的粪便糖皮质激素测量值。来自混合样本的粪便糖皮质激素代谢物估计值的变异性低于使用来自同一粪便团块的粪粒组的糖皮质激素代谢物测量值，尽管这些差异无统计学意义（低浓度组：F = 0.59；自由度 = 1,38；P = 0.45；中浓度组：F = 0.13；自由度 = 1,34；P = 0.72；高浓度组：F = 2.30；自由度 = 1,28；P = 0.14）。所有处理组和采样方法的平均变异系数<10%。然而，一项功效分析表明，与粪粒组相比，混合子样本技术检测统计学显著差异所需的样本更少。我们的结果表明，糖皮质激素代谢物在白尾鹿粪便中可能分布不均。因此，仅从粪便团块中选取少数粪粒可能会使检测结果的解释产生偏差。我们建议研究人员在取出粪便材料子样本进行分析之前，先将整个粪便团块均质化。此外，在解释粪便糖皮质激素研究结果时，必须考虑其他变异来源。
