Abstract
BackgroundNumbers of giraffes are declining rapidly in their native habitat. As giraffe research and conservation efforts increase, the demand for more complete measures of the impact of conservation interventions and the effects of captive environments on animal health and welfare have risen. We compared the ability of six different enzyme immunoassays to quantify changes in fecal glucocorticoid metabolites (FGM) resulting from three sources: adrenocorticotropic hormone stimulation test, transport, and time of day that samples were collected.ResultsTwo male giraffes underwent ACTH injections; all six assays detected FGM increases following injection for Giraffe 1, while only three assays detected FGM increases following injection for Giraffe 2. Consistent with other ruminant species, the two 11-oxoetiocholanolone assays (one for 11,17-dioxoandrostanes and the other for 3α,11-oxo metabolites) measured the most pronounced and prolonged elevation of FGM, while an assay for 3β,11β-diol detected peaks of smaller magnitude and duration. Both of the 11-oxoetiocholanolone assays detected significant FGM increases after transport in Giraffes 3–7, and preliminary data suggest FGM detected by the assay for 11,17-dioxoandrostanes may differ across time of day.ConclusionsWe conclude the assay for 11,17-dioxoandrostanes is the most sensitive assay tested for FGM in giraffes and the assay for FGM with a 5β-3α-ol-11-one structure is also effective. 11-oxoetiocholanolone enzyme immunoassays have now been demonstrated to be successful in a wide variety of ruminant species, providing indirect evidence that 5β-reduction may be a common metabolic pathway for glucocorticoids in ruminants. As FGM peaks were detected in at least some giraffes using all assays tested, giraffes appear to excrete a wide variety of different FGM. The assays validated here will provide a valuable tool for research on the health, welfare, and conservation of giraffes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-016-0864-8) contains supplementary material, which is available to authorized users.
Highlights
Numbers of giraffes are declining rapidly in their native habitat
One sample from Giraffe 2 was stored on ice for almost 2 h, which could have affected fecal glucocorticoid metabolites (FGM) [29, 39], but Transport As samples from the transported giraffes were collected once per day and only the two 11-oxoetiocholanolone enzyme immunoassays (EIAs) identified peaks lasting more than 24 h following Adrenocorticotropic hormone (ACTH) challenge, we selected these two EIAs to assess the influence of transportation on FGM levels
As the dose of ACTH used in these challenges was on the low end of the range used in other published challenges (1 and 0.7 IU/kg here; 0.5 to 12.5 IU/kg in [42]; 0.5 to 31 IU/kg in [43]), and ACTH was administered over a span of less than 2 min, the resulting increase in glucocorticoid hormones (GC) would be expected to be of shorter duration and perhaps lower intensity than those seen in other ACTH challenge studies
Summary
As giraffe research and conservation efforts increase, the demand for more complete measures of the impact of conservation interventions and the effects of captive environments on animal health and welfare have risen. Wild populations have recently suffered major declines, from an estimated 140,000 individuals to an estimated 80,000 individuals over the course of a decade, and two Studies of wild populations are revealing that giraffes have complex social structures and habitat dynamics with implications for conservation strategies [4,5,6,7]. The adrenal system plays a role in energy regulation [18], reproduction [19], immune function [20], and physiological responses to disturbance [21], so an efficient and ideally noninvasive measure of adrenal responses in giraffes could shed important light on population dynamics, conservation efforts, health, and welfare in both in and ex situ populations. To the best of our knowledge no data are currently available on hypothalamic-pituitary-adrenal (HPA) axis functioning in giraffes
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