title: Fecal estrogen, progestagen and glucocorticoid metabolites during the estrous cycle and pregnancy in the giant anteater (Myrmecophaga tridactyla): evidence for delayed implantation.
abstract: BACKGROUND
  Declining numbers of wild giant anteaters highlight the importance of sustainable captive populations. Unfortunately, captive reproductive management is limited by the lack of external physical indicators of female reproductive status and the aggressive behavior of males. We examined the endocrinology of the estrous cycle and pregnancy, and whether delayed implantation is a gestational strategy for giant anteaters as described for other xenarthrans.
  
  
  METHODS
  Feces were collected from seven captive females 3-5 times weekly and mating was recorded. Concentrations of estrogen (estrone-glucuronide, E1, and estradiol-17β, E2), progestagen (20-oxo-progestagens, P4), and glucocorticoid (GC) metabolites were examined in fecal extracts by enzyme immunoassay.
  
  
  RESULTS
  Estrous cycles for nulliparous females (6 cycles, n = 2) compared to the multiparous female (6 cycles, n = 1) were shorter (47.3 +/- 4.3 days versus 62.5 +/- 2.6 days) with relatively lower luteal phase concentrations of P4 (49.4 +/- 2.9 ng/g versus 136.8 +/- 1.8 ng/g). The four remaining females had unclear ovarian activity: two females exhibited apparent luteal activity but unclear fluctuations in estrogens, while the other two females had parallel fecal P4 and estrogens concentrations. Pregnancy ranged 171-183 days with females returning to estrus post-partum as early as 60 days (n = 3, 1.8-4 years of age at mating). Delayed implantation was indicated by a biphasic elevation in fecal P4 metabolites: the initial 4-fold increase occurred for 81-105 days and was followed by a 26-fold secondary rise in P4 metabolites lasting 66-94 days prior to parturition. Fecal GC was correlated with fecal estrogens and greatest during estrus, late pregnancy, and six days prior to parturition (estrous cycle GC, 14.4-62.8 ng/g; pregnancy GC, 13.6-232.7 ng/g).
  
  
  CONCLUSIONS
  Estrous cycles of giant anteaters occurred year-round, but were shorter and more intermittent in younger nulliparous animals compared to a multiparous female. A pronounced elevation in fecal P4, estrogen, and GC occurred during late gestation after an initial post-mating delay providing evidence for delayed implantation. Adrenocorticoid activity indicated impending parturition. Differences in estrous cycle characteristics with age and the protracted but variable gestation length must be considered to improve reproductive success and neonatal survival in giant anteaters.
authors: Department of Conservation and Research, Memphis Zoo, 2000 Prentiss Place, Memphis, Tennessee, USA. kknott@memphiszoo.org.
authors: Katrina K
authors: KK
authors: Knott
authors: Beth M
authors: BM
authors: Roberts
authors: Morgan A
authors: MA
authors: Maly
authors: Carrie K
authors: CK
authors: Vance
authors: Jennifer
authors: J
authors: Debeachaump
authors: Jackie
authors: J
authors: Majors
authors: Peter
authors: P
authors: Riger
authors: Heather
authors: H
authors: Decaluwe
authors: Andrew J
authors: AJ
authors: Kouba
mesh_terms: D000367:Age Factors; D000818:Animals; D010064:Embryo Implantation / Q000502:physiology*; D004967:Estrogens / Q000378:metabolism; D030762:Estrous Cycle / Q000378:metabolism*; D005243:Feces / Q000737:chemistry; D005260:Female; D005938:Glucocorticoids / Q000378:metabolism; D006728:Hormones / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D011372:Progestins / Q000378:metabolism; D004490:Xenarthra / Q000378:metabolism* / Q000502:physiology
chemical_list: D004967:Estrogens; D005938:Glucocorticoids; D006728:Hormones; D011372:Progestins
references: Reprod Biol Endocrinol. 2012 Nov 30;10:102
references: 23199198
references: Theriogenology. 1998 Jul 15;50(2):237-48
references: 10734491
references: Anim Reprod Sci. 2000 Jul 2;60-61:571-81
references: 10844225
references: Anim Reprod Sci. 1998 Oct;53(1-4):209-19
references: 9835377
references: Biol Lett. 2012 Oct 23;8(5):695-7
references: 22219389
references: Biol Reprod. 1981 Aug;25(1):128-33
references: 6456777
references: Anim Reprod Sci. 1998 Oct;53(1-4):173-90
references: 9835375
references: J Reprod Fertil. 1978 Sep;54(1):133-6
references: 712700
references: Gen Comp Endocrinol. 2011 May 1;171(3):283-92
references: 21354160
references: Zoo Biol. 2011 Mar-Apr;30(2):212-7
references: 21462248
references: Proc Natl Acad Sci U S A. 2006 Feb 28;103(9):3203-8
references: 16492730
references: Annu Rev Physiol. 2000;62:353-75
references: 10845095
references: Biol Reprod. 1996 Oct;55(4):844-53
references: 8879499
references: Reproduction. 2010 Jul;140(1):183-93
references: 20406954
references: Reproduction. 2009 Dec;138(6):979-86
references: 19692498
references: Lab Anim Sci. 1976 Jun;26(3):501-4
references: 940314
references: Q Rev Biol. 1990 Mar;65(1):23-42
references: 2186428
references: Reproduction. 2004 Dec;128(6):669-78
references: 15579584
references: Anim Reprod Sci. 2009 Dec;116(3-4):358-69
references: 19304417
references: Biol Reprod. 1994 Oct;51(4):776-86
references: 7819459
references: Gen Comp Endocrinol. 2000 Dec;120(3):260-75
references: 11121291
references: Clin Chem. 1991 Jun;37(6):838-44
references: 2049848
references: Gen Comp Endocrinol. 2012 Aug 1;178(1):64-74
references: 22537671