Steroid metabolism and validation of noninvasive endocrine monitoring in the African wild dog (Lycaon pictus)
Publication Type: |
Journal Article |
Year of Publication: |
1997 |
Authors: |
S. L. Monfort, S. K. Wasser, K. L. Mashburn, M. Burke, B. A. Brewer, S. R. Creel |
Publication/Journal: |
Zoo Biology |
Publisher: |
A Wiley Company, Inc., Wiley Subscription Services |
Keywords: |
estrogens, fecal steroids, hormones, progesterone metabolites, testosterone, urinary steroids |
ISBN: |
1098-2361 |
Abstract:
Abstract 10.1002/(SICI)1098-2361(1997)16:6<533::AID-ZOO6>3.3.CO;2-W The purpose of this study was to validate noninvasive endocrine monitoring techniques for African wild dogs (Lycaon pictus) and to establish physiological validity of these methods by evaluating longitudinal reproductive-endocrine profiles in captive individuals. To determine the primary excretory by-products of ovarian steroid metabolism, [14C]-progesterone and [3H]-estradiol were co-administered to a female and all excreta were collected for 80 hr postinjection. Radiolabel excretion peaked ≤ 18 hr postinfusion, and progesterone and estradiol metabolites were excreted in almost equivalent proportions in urine (39.7 and 41.1%, respectively) and feces (60.3 and 58.9%, respectively). Most of the urinary metabolites were conjugated (estradiol, 94.3 ± 0.3%; progesterone, 90.4 ± 0.5%), so that immunoassays for pregnanediol-3α-glucuronide (PdG) and estrogen conjugates (EC) were effective for assessing steroid metabolites. Two immunoreactive estrogens (estradiol and estrone) and at least one immunoreactive progesterone metabolite (3α-hydroxy-5α, pregnan-20-one) were detected in feces. Urine and fecal samples were collected (1–3 times per week) for 1.5 yr from one adult female and two adult males to assess longitudinal steroid metabolite excretion. Overall correlation of urinary PdG to matched, same-day fecal progesterone metabolites immunoreactivity was 0.38 (n = 71, P < 0.05). Similarly, urinary EC was correlated (P < 0.05) with same-day fecal estrogen immunoreactivity (r = 0.49, n = 71). During pregnancy and nonpregnant cycles, copulation occurred at the time of peak (or declining) estrogen metabolites and increasing progesterone metabolites concentrations. Estrus duration was 6–9 days and gestation lasted 69 days with parturition occurring coincident with a drop in progesterone metabolites. Males exhibited seasonal trends in fecal testosterone excretion with maximal concentrations from July to September coincident with peak mating activity. Although these limited longitudinal hormone profiles should be interpreted cautiously, noninvasive gonadal steroid monitoring suggests that: (1) both female and male wild dogs may exhibit reproductive seasonality in North America, (2) females are monoestrous, and (3) peak testicular activity occurs between August and October coincident with mating behavior. From a conservation perspective, noninvasive endocrine monitoring techniques should be useful for augmenting captive breeding programs, as well as for developing an improved understanding of the physiological mechanisms underlying reproductive suppression in response to social and ecological pressures. Zoo Biol 16:533–548, 1997. © 1997 Wiley-Liss, Inc.