Characterization of reproductive cycles and adrenal activity in the black‐footed ferret (Mustela nigripes) by fecal hormone analysis

Abstract

The reproductive cycle of the black-footed ferret (Mustela nigripes) was characterized by enzyme immunoassay (EIA) analysis of ovarian fecal steroids (estradiol, progestins) in 29 females over two consecutive breeding seasons. Estrous status was determined by measuring the vulva size and examining the percentage of superficial cells in vaginal lavages. Mean fecal estradiol concentrations were correlated with vulval area (r = 0.370, P < 0.0001) and the percentage of superficial cells (r = 0.380, P < 0.0001). Ovulation resulted in a rise in fecal progestin concentrations 5 days after breeding that differed (P < 0.05) between pregnant (n = 14) and pseudopregnant (n = 12) females during the late luteal phase (days 12-40), with concentrations remaining higher in pregnant animals. Gestation length was 41.3 ± 0.7 days with 3.6 ± 0.4 kits produced per female. Litter size correlated significantly (P < 0.05) with fecal estradiol, but not progestins during the 12 to 40 days after breeding. Females failing to breed (n = 3) remained in estrus for 31 ± 6.2 days before ovulation induction with human chorionic gonadotropin. Adrenal activity in male (n = 4) and female (n = 6) black-footed ferrets was monitored by quantifying fecal corticoid metabolites after a series of manipulations (physical restraint, intramuscular saline, intramuscular gel adrenocorticotropic hormone (ACTH), intramuscular liquid ACTH). A significant (P < 0.0001) increase in fecal corticoids above the pre-treatment baseline occurred 20 to 44 hours after restraint (five of 10 animals), saline (six of nine), gel ACTH (seven of 10), and liquid ACTH (nine of 10) treatments. Immunoreactivity of high-performance liquid chromatography-separated fecal elutes was compared using antibodies against cortisol and corticosterone. The cortisol EIA demonstrated immunoreactivity that co-eluted with 3 H-cortisol, whereas a corticosterone radioimmunoassay detected a metabolite peak that coeluted with 3 H-corticosterone in addition to a slightly less polar and one considerably more polar peak. Despite recognizing different metabolites, both assays produced similar temporal profiles of corticoid excretion after manipulation. This study provides new information on the black-footed ferret regarding differences in fecal steroid excretion patterns between pregnancy and pseudopregnancy and the potential application of fecal corticoid metabolite monitoring for evaluating responses to stressors associated with practices used in breeding management.

A Validation of Extraction Methods for Noninvasive Sampling of Glucocorticoids in Free‐Living Ground Squirrels

“…Here, ACTH increased fecal metabolite concentrations 0.5-2.5 times, and DEX reduced metabolite concentrations 0.25-0.5 times relative to baseline values, revealing modest but significant physiological responses to the treatments. These responses are similar to the moderate effects of ACTH reported for some ferrets, rhinoceroses, and chinchillas Young et al 2001;Ponzio et al 2004). As additional studies utilize exogenous glucocorticoid stimulants or suppressors, patterns of differential response as a function of species, population, sex, or individual will become more clear (Hubbs et al 2000;Teskey-Gerstl et al 2000;Brown et al 2001;Goymann et al 2001;Hik et al 2001;Young et al 2001).…”

“…5, 7). In ACTH and DEX studies with hyenas, common marmosets, and ferrets, some nonresponsive individuals were also observed (Goymann et al 1999;Saltzman et al 2000;Young et al 2001). A nonresponsive profile may reflect a history of chronic stress (e.g., competition for territories, unpredictable weather, or low food availability) or an alteration of glucocorticoid receptors.…”

“…In large mammals, an increase in fecal metabolite levels can be detected approximately 24-48 h after an ACTH challenge (Graham and Brown 1996;Monfort et al 1998;Goymann et al 1999;Wasser et al 2000;Brown et al 2001;Millspaugh et al 2002;Wielebnowski et al 2002;Mashburn and Atkinson 2004;Young et al 2004). In smaller mammals (<150 g), fecal glucocorticoid-metabolite levels typically increase within 24 h of stimulation of the adrenal glands or injection of labeled glucocorticoids (e.g., 6-12 h in house mice, deer mice, and red-backed voles [Harper and Austad 2000]; 8-24 h in common marmosets [Bahr et al 2000]; 20-44 h in black-footed ferrets [Young et al 2001]; 30 h in chinchillas [Ponzio et al 2004]). …”

Physiological Stress Responses, Fecal Marking Behavior, and Reproduction in Wild European Pine Martens (Martes martes)

“…The quantification of glucocorticoids and SSHs in blood and urine requires capture and manipulation of animals which, in itself, can modify hormonal concentrations and lead to increases in physiological stress (Young et al, 2001). Quantification of these hormones in feces is a noninvasive method that is increasingly used in carnivore studies (e.g., Goymann et al, 2001;Soto et al, 2004;Creel, 2005;Barja et al, 2008a, b).…”

Non-invasive measurement of fecal estrogens in the spotted hyena (Crocuta crocuta)

“…Fecal steroid analysis, in particular, offers an attractive alternative to blood sampling in both wild and captive animals. For collecting samples frequently, non-invasively, and without disrupting normal behavior of individuals or groups, techniques have been developed to assay fecal estrogen concentrations in a number of other mammalian carnivores (Brown et al, 1994;Monfort et al, 1997;Onuma et al, 2002;Shille et al, 1984;Young et al, 2001). A preliminary study in captive Crocuta detected measurable amounts of radiolabeled estrogen in fecal matter, and indicated that feces, rather than urine, should prove useful for sampling of excreted steroid hormones (Koretz, 1992).…”