Validation of a fecal glucocorticoid metabolite assay for collared peccaries (Pecari tajacu)

The possibility of assessing endogenous adrenal activity in the collared peccary (Pecari tajacu) was tested by using an adrenocorticotropic hormone (ACTH) challenge in a fecal glucocorticoid metabolite (FGM) assay. Feces were collected from 12 captive adult male peccaries beginning 48 hr prior to challenge; six of these animals received the challenge as an ACTH injection and the other six were injected with saline solution. Feces collection ended 120 hr after injections. As a control, feces were collected for eight consecutive days from another six adult male peccaries that remained in their original mixed-sex herds in semiconfined paddocks. All feces samples were freeze-dried, extracted by an ethanol vortex method, and assayed for glucocorticoids by means of an enzyme immunoassay. FGM concentrations were compared between the treatments by a repeated measures analysis of variance (ANOVA) followed by a post hoc Tukey test. The assay is reliable but, instead of the usual proportion of 1:50 in ethanol (fecal mass:solvent), 1:10 is recommended for best extraction of FGM. Baseline FGM concentrations were similar among the ACTH, saline, and control treatments (29.7 +/- 11.2 ng/g(-1) dry feces) during the 48 hr before the challenge. The ACTH group reached an FGM excretion peak at 24 hr post-treatment, followed by a decline, while in the control and saline groups FGM levels remained relatively constant. Therefore, the fecal glucocorticoid metabolite assay reflects endogenous adrenal activity in the collared peccary and is a powerful tool for noninvasive stress monitoring in peccaries.