Department of Zoology, Michigan State University, East Lansing, MI 48824, USA.
Gen Comp Endocrinol. 2011 Nov 1;174(2):124-31. doi: 10.1016/j.ygcen.2011.08.010. Epub 2011 Aug 19.
A growing number of longitudinal studies in free-ranging animals are measuring fecal steroid hormone metabolite concentrations (FHM). Free-ranging animals can exhibit major seasonal changes in their diet, yet we know relatively little about how diet affects FHM. We experimentally manipulated the diets of female and male North American red squirrels (Tamiasciurus hudsonicus) to determine how diet affected fecal cortisol (FCM) and androgen (FAM) metabolite concentrations. We measured FCM using an enzyme immunoassay (EIA) that we have previously validated and measured FAM using an assay we have previously validated for use in females and validate for males herein. We validated our EIA to measure FAM in males by identifying that 44.5±0.05% of recovered radiolabeled testosterone was excreted in the feces, our EIA antibody detected the fecal testosterone metabolites, and males with scrotal testes had significantly higher FAM (3.02±0.06 lnng/g dry feces) than those with abdominal testes (2.73±0.06). We initially fed all squirrels the same diet, but then switched one group of squirrels to a diet consisting of conifer seed (n=4 squirrels) whereas the other group was switched to peanut butter (n=7). FCM and FAM in squirrels fed conifer seed significantly increased from 0 to 94 h after their diets were changed. FCM in squirrels fed peanut butter significantly declined, whereas FAM declined but not significantly. This demonstrates that change in dietary fiber consumption (peanut butter versus conifer seed) or even slight differences in diet (conifer versus sunflower seeds) can strongly influence FHM.
越来越多的野生动物自由放养研究正在测量粪便类固醇激素代谢物浓度（FHM）。自由放养的动物在饮食方面可能会出现重大的季节性变化，但我们对饮食如何影响 FHM 知之甚少。我们通过实验操纵雌性和雄性北美的红松鼠（Tamiasciurus hudsonicus）的饮食，以确定饮食如何影响粪便皮质醇（FCM）和雄激素（FAM）代谢物浓度。我们使用之前经过验证的酶免疫分析（EIA）测量 FCM，并使用之前在雌性中经过验证且在此处为雄性验证的测定法测量 FAM。我们通过鉴定出 44.5±0.05%回收的放射性标记睾丸激素在粪便中排泄，我们的 EIA 抗体检测到粪便中的睾丸激素代谢物，以及具有阴囊睾丸的雄性的 FAM（3.02±0.06 lnng/g 干粪便）显著高于具有腹部睾丸的雄性（2.73±0.06），从而验证了我们的 EIA 可以测量雄性的 FAM。我们最初让所有松鼠都吃相同的饮食，但后来将一组松鼠的饮食改为松籽（n=4 只松鼠），而另一组松鼠则改为花生酱（n=7）。食用松籽的松鼠的 FCM 和 FAM 在饮食改变后 0 到 94 小时内显著增加。食用花生酱的松鼠的 FCM 显著下降，而 FAM 虽然下降但不显著。这表明膳食纤维摄入量的变化（花生酱与松籽），甚至是饮食的细微差异（松籽与葵花籽）都可以强烈影响 FHM。
