Urinary steroid evaluations to monitor ovarian function in exotic ungulates: VII. Urinary progesterone metabolites in the Equidae assessed by immunoassay

A direct enzyme immunoassay (EIA) for non-specific urinary progesterone (Po) metabolites, utilizing a non-specific monoclonal antibody against pregnanediol-3-glucuronide, was evaluated for the purpose of assessing luteal function in equids. Urinary pregnanediol-3-glucuronide (PdG) and immunoreactive PdG-like conjugate (iPdG) concentrations, indexed by creatinine, were compared to plasma Po concentrations in non-conceptive ovarian cycles through two ovulations in four mares. High-performance liquid chromatography (HPLC) of urine from lutealphase mares and a pregnant zebra revealed an absence of significant concentrations of PdG and the presence of at least three immunoreactive compounds, all of which were more polar than PdG. The concentration of iPdG in the mare ranged from a nadir of approximately 3 ng/mg Cr at the time of ovulation to nearly 400 ng/mg Cr at the mid-luteal-phase peak and paralleled plasma Po concentrations. This non-radiometric assay for iPdG permits the assessment of ovulation, luteal formation and function, and luteolysis in unprocessed urine samples from domestic mares. Data from a single zebra indicate this approach also will permit simplified and non-invasive longitudinal studies of ovarian function among a wide range of Equidae.     

Probably never human. Review of chimpanzee material culture: Implications for human evolution,by W.C. McGrew. Cambridge,U.K., Cambridge University Press, 1992, 277 pp, $79.95, cloth

Pregnanediol-3α-glucuronide (PdG) was measured in the urine of six Goeldi's monkeys during pregnancy and the postpartum period. A stress-free, non-invasive urine sampling technique permitted frequent collection of urine from members of the breeding group. A comparison of the periovulatory profiles of PdG and estrone conjugates revealed close agreement. The day of ovulation was defined as that immediately preceding a 2-4 day period with two consecutive urine samples for which the PdG content was in excess of 0.20 μg/mg Cr and 0.40 μg/mg Cr, respectively. In urine samples collected from parturition to the next ovulation, 70.9% of the PdG-values were below 0.20 μg/mg Cr, whereas 99.2% of the urinary PdG concentrations measured during pregnancy were greater than this “threshold concentration”. A conception cycle was therefore defined as one in which the concentration of urinary PdG remained above 0.20 μg/mg Cr in all urine samples collected between day 1 and day 20 after ovulation. Gestation length was 151.5 ± 1.6 days (mean ± SEM, n = 6; range 147-157 days). The postpartum ovulation occurred 22.6 ± 4.7 days (mean ± SEM, n = 9; range 11-53 days) following birth. With the exception of two non-conception postpartum cycles observed in one female, with inter-ovulatory intervals of 26 and 27 days, postpartum ovulation resulted in conception, giving a 77.8% conception rate for nine observed cycles. The simple and rapid radioimmunoassay used in this study requires 5 h from urine collection to the final result, hence permitting daily monitoring of a large sample of females. It thus has important potential for conservation breeding programs and for other scientific investigations carried out with this endangered primate species. © 1994 Wiley-Liss, Inc.     

Assessment of female reproductive status in captive-housed Hanuman langurs (Presbytis entellus) by measurement of urinary and fecal steroid excretion patterns

The study reports on the use of urinary and fecal hormone measurements for monitoring female reproductive status in captive-housed Hanuman langurs (Presbytis entellus). Matched urine and fecal samples collected throughout 7 complete menstrual cycles of two females, and during part of one pregnancy in a third female were analyzed. Estrone conjugates (E1C) and immunoreactive pregnanediol glucuronide (PdG) in urine and immunoreactive estradiol (E2), progesterone (P4), pregnanediol (Pd) and 20α-hydroxyprogesterone (20αOHP) in feces were measured by enzymeimmunoassay. E1C and PdG in urine were excreted in a cyclic pattern with E1C levels increasing 3- to 4-fold during the follicular phase to reach preovulatory peak values 2 days before a defined rise in PdG concentrations. Cycle lengths ranged between 20 and 34 days comprising a variable follicular phase of 7–21 days and a more consistent luteal phase of 12–14 days. High pressure liquid chromatography (HPLC) analysis of fecal extracts confirmed the presence of all fecal hormones measured, but indicated large amounts of additional immunoreactivity in the three progestin assays. The patterns of excretion of fecal E2 and all three fecal progestins corresponded well with those of steroid metabolites in urine in showing a clear and well defined follicular phase E2 rise followed by a luteal phase progestin increase. Measurement of 20αOHP immunoreactivity revealed the most stable baseline and the highest follicular/luteal phase differential. Levels of all hormones were clearly elevated during pregnancy although urinary E1C and PdG showed a more pronounced increase compared to fecal metabolites. The results indicate that urinary and fecal hormone analysis can be applied to noninvasive monitoring of reproductive status in the Hanuman langur. © 1995 Wiley-Liss, Inc.     

Urinary steroids in the periparturient and postpartum periods through early pregnancy in llamas

Urinary steroids were determined daily in the periparturient and postpartum periods, including early pregnancy, in the female llama. Estrone sulfate (E(1)S) and pregnanediol glucuronide (PdG) concentrations were determined by enzyme immunoassay with values corrected for variations in urine concentration by creatinine. Estrone sulfate concentrations, elevated during the last 20 days of gestation through 12 hours before parturition, were declining at the time of delivery. Pregnanediol glucuronide concentrations followed a pattern similar to that of estrone sulfate except that values began to decrease 5 days before parturition. Values for both E(1)S and PdG were basal by 24 hours after delivery. The first significant elevation of estrone sulfate, indicative of initial follicle development, was observed 5 days after parturition. Pregnanediol glucuronide concentrations were low during the postpartum period until 4 to 5 days after breeding. The PdG values rose steadily following copulatory-induced ovulation, which was initiated at about 2 weeks postpartum; values continued to increase through the first 15 days of pregnancy.     

Induction of luteal regression in the marmoset monkey (Callithrix jacchus) by a gonadotrophin-releasing hormone antagonist and the effects on subsequent follicular development

Doses of 100 or 200 micrograms of a novel GnRH antagonist ([N-acetyl-D beta Na11-D-pCl-Phe2-D-Phe3-D-Arg6-Phe7-Arg8-D-Ala10]NH2 GnRH) (4 animals/dose) were administered on Days 10/11 of the luteal phase and induced a marked suppression of circulating bioactive LH and progesterone concentrations within 1 day of treatment (P less than 0.01). Thereafter, progesterone concentrations remained low or undetectable until after the next ovulation. Similar results were obtained when 200 micrograms antagonist were given on Days 5/6 of the luteal phase (N = 4). The interval from injection of antagonist (200 micrograms but not 100 micrograms) to ovulation (based on a rise in progesterone above 10 ng/ml) was significantly longer than that from prostaglandin-induced luteal regression to ovulation in control cycles (N = 4/treatment) (range, 13-15 days after antagonist vs 8-10 days after prostaglandin, P less than 0.01). This delay of 4-5 days was equivalent to the duration for which LH concentrations were significantly suppressed by 200 micrograms antagonist when administered to ovariectomized animals (N = 3). Corpus luteum function during the cycle after GnRH antagonist treatment appeared normal according to the pattern of circulating progesterone. These results show that corpus luteum function and preovulatory follicular development in the marmoset monkey are dependent on pituitary gonadotrophin secretion.     

Long-term data on basic reproductive parameters and evaluation of endocrine,morphological, and behavioral measures for monitoring reproductive status in a group of semifree-ranging Tonkean macaques (Macaca tonkeana)

Cycle and gestation lengths, menstruation patterns, female genital swelling characteristics, and male-female consortship durations are reported in a semifree-ranging group of Tonkean macaques (Macaca tonkeana) studied over a 12 year period. In addition, profiles of urinary estrone conjugates (E1C) and immunoreactive pregnanediol glucuronide (PdG) throughout four complete menstrual cycles in two females and three full-term pregnancies are presented. Based on intermenstrual intervals, a mean cycle length of 37–41 days (n = 55 cycles in 10 females) was found. Gestation length averaged 173 days (n = 27 pregnancies in eight females). Measurement of PdG immunoreactivity in urine revealed a cyclic pattern with a 5–15-fold increase between follicular and luteal phase concentrations, suggesting that PdG is a reliable indicator of ovarian cyclicity and luteal function. In contrast to PdG, E1C excretion showed no clear pattern throughout the cycle; however, highest values of E1C were usually found shortly before the onset of the luteal phase PdG rise at the presumed time of ovulation. Levels of both hormones were elevated during the first half of gestation and showed a marked increase throughout the second half, with maximum E1C concentrations being up to 100-fold higher than nonpregnant levels. Consortships by the male and occurrence of female genital swelling were long lasting (on average 5–10 days and 13 days, respectively) and were restricted to the follicular phase of the cycle. The day of maximal swelling and day of detumescence as well as the end of male consortship were closely associated with the periovulatory period. Swellings and consortships were longer following lactational ammenorhea than for subsequent cycles. The evolutionary significance of the cyclical changes undergone by females upon their relations with males is discussed. © 1996 Wiley-Liss, Inc.     

Steroidogenic and morphological characteristics of granulosa and thecal compartments of the differentiating rabbit corpus luteum in culture

On the day after ovulation, the thecal tissue and associated mural granulosa lutein cells of the rabbit corpus luteum were separated from the granulosa lutein 'core' by dissection and these tissues were cultured separately or together (whole corpus luteum) in defined medium for 10 days on stainless-steel grids. The medium was changed completely every 24 h. Replicate tissues were cultured with testosterone (10 ng/ml), but no other hormones were added to the medium. Progesterone production increased during the first 2 days of culture for whole corpus luteum, granulosa lutein cells and the thecal compartment which also included granulosa lutein cells. After 3 days, the production of progesterone declined gradually, but was still detectable on Day 10. The production of the metabolite, 20 alpha-dihydroprogesterone, by whole corpus luteum was equal to or greater than that of progesterone. Without the addition of testosterone, the granulosa lutein cells produced little (10 pg/culture) oestradiol during 1 day of culture, but the thecal compartment and whole corpus luteum each produced about 100 pg/culture on Day 1 and declining quantities over the next 2 days. In the presence of testosterone added to the medium, the formation of oestradiol was greatly increased for all tissues for 5-6 days of culture, after which time oestradiol was no longer detectable with or without testosterone in medium. Transmission electron microscopy of cells after 10-12 days of culture revealed fine structure that is characteristic of luteal cells, including abundant smooth endoplasmic reticulum, lipid droplets, and junctions between the luteal cells. The corpus luteum in culture resembles the corpus luteum in situ in that steroidogenesis and differentiation can proceed for a period after ovulation without extrinsic hormonal stimulation.     

Describing Ovarian Cycles,Pregnancy Characteristics,and the Use of Contraception in Female White‐Faced Marmosets,Callithrix geoffroyi

Endocrine data and characteristics of nonconceptive ovarian cycling and pregnancy are limited within the genus Callithrix to the common marmoset (C. jacchus) and Wied's black tufted‐ear marmoset (C. kuhlii). This article presents patterns of urinary pregnanediol‐3‐glucuronide (PdG) excretion, as determined by enzyme immunoassay, throughout the course of ovarian cycling and pregnancy in white‐faced marmosets (C. geoffroyi). Furthermore, characteristics of reproductive parameters including litter size, duration of gestation, maternal age, and information about ovarian cycling following administration of contraceptives are also described. A steep increase in PdG, an indication of ovulation, characterizes normative ovarian cycles, with peak‐to‐peak intervals between cycles being 27.82 ± 1.49 days in length. PdG excretion (μg/mg Cr) across pregnancy peaked during the 1st and 2nd trimesters (1st = 20.71 ± 2.98, 2nd = 21.16 ± 2.60) and declined gradually to near preconception levels over the 3rd trimester until parturition (3rd = 5.74 ± 1.60). Gestation lasted 148.55 ± 1.89 days. Most pregnancies (82.8%) resulted in an immediate postpartum ovulation (PPO) of 17.45 ± 2.22 days with 58.3% of PPOs resulting in conception. No differences in PdG excretion during the 1st trimester between full pregnancies and miscarriages were found, and pregnancy characteristics such as litter size, duration of gestation, and maternal age were not associated with PdG concentrations. Administration of cloprostenol resulted in shorter peak‐to‐peak cycle durations, but ovulation was detectable with similar concentrations of peak PdG to a normal nonconceptive cycle. Conversely, medroxyprogesterone acetate (DMPA) injections resulted in little to no PdG excretion across the ovarian cycle. Both methods of contraception providing effective prevention of conception. Overall, these results show that strong similarities in reproductive parameters persist within the genus Callithrix and to a lesser extent across the Callitrichidae family. Am. J. Primatol. 74:1044‐1053, 2012. © 2012 Wiley Periodicals, Inc.     

Effects of oestradiol implants on the ovulation rate of the ewe

In a series of 5 experiments, ewes were treated with implants releasing oestradiol-17 beta and the effects on ovulation rate were observed. Large doses of oestradiol-17 beta (greater than 20 micrograms/day) produced anovulation while smaller amounts only reduced the proportion of twin ovulations. Amounts of exogenous oestradiol comparable to ovarian production rate in the luteal phase (less than 1 microgram/day) produced a significant (P less than 0.01) suppression in ovulation rate. Treatment during the follicular phase of the oestrous cycle was most effective, but treatment during the luteal phase alone also appeared to suppress ovulation rate. Furthermore, in 2 of 3 experiments ewes treated with low amounts of oestradiol during the first half of the luteal phase were less likely to have multiple ovulations at the subsequent oestrous period. The results support the hypothesis that oestrogen is involved in the physiological control of ovulation rate in the ewe, but this action is probably not restricted to the assertion of dominance by a maturing follicle during the follicular phase.     

Urinary steroid evaluations to monitor ovarian function in exotic ungulates: II. Comparison between the giraffe (Giraffa camelopardalis) and the Okapi (Okapia johnstoni)

Ovarian activity in the female giraffe was evaluated during the nonfertile ovarian cycle and during the terminal stages of gestation. Progesterone metabolites, in the form of pregnanediol-3-glucuronide (PdG), were measured in daily random urine samples collected from four adult parous giraffes. The follicular phase averaged 4.0 ± 0.1 days in length (N = 12; range 3–5 days) and peak PdG levels in the postovulatory period averaged 30.9 ± 1.7 ng/mg Cr (N = 12). PdG levels during the latter half of gestation greatly exceeded average luteal phase levels, which is in contrast to domestic ruminants. Prior to parturition, a marked decline in PdG excretion was evident, which may be useful for anticipating this event. These data serve to elucidate ovarian function in the mature female giraffe and to provide information concerning the physiologic role of certain anomalous ovarian structures. In addition, observed similarities in the pattern of PdG excretion during the nonfertile cycles of the giraffe and the okapi indicate similar underlying physiologic processes.     

Oestrous cycle of the North American bison (Bison bison) characterized by urinary pregnanediol-3-glucuronide.

An enzyme immunoassay for urinary pregnanediol-3 alpha-glucuronide (PdG) was evaluated for the indirect measurement of progesterone metabolites during the oestrous cycle and early pregnancy of uncaptured North American bison. Comparisons between plasma progesterone and urinary PdG, dose-response parallelism between the standard curve and diluted urine samples and high-performance liquid cochromatography revealed that PdG was a primary immunoreactive urinary metabolite of progesterone in bison. Urine samples were collected directly from the soil from 29 bison cows during the August rutting season and analysed for PdG. Eight bison cows demonstrated complete oestrous cycles ranging from 19 to 26 days (mean cycle length = 23.12 +/- 0.76 days) and behavioural oestrus among four of these cows correlated with PdG nadirs. Mean PdG nadirs were 63.62 +/- 21.61 ng/mg urinary creatinine (Cr) and mean peak midluteal values were 546.01 +/- 130.73 ng/mg Cr. Seven of eight became pregnant, indicating that bison exhibit a second seasonal oestrus. Eighteen other bison cows were pregnant prior to the beginning of the study and demonstrated non-cyclic increased PdG concentrations (greater than 200 ng/mg Cr) during the 30-day course of collection. Three cows ovulated and became pregnant during the 30-day collection period and then exhibited increasing urinary PdG concentrations. This report demonstrates that ovarian function in uncaptured bison can be monitored by means of urinary PdG and that both ovulatory cycles and early pregnancy can be detected.     

Gonadotropin-releasing hormone treatment induces follicular growth and ovulation in seasonally anestrous mares

A study was conducted to evaluate the effectiveness of gonadotropin-releasing hormone (GnRH) pulse infusion to stimulate follicular development and induce ovulation in seasonally anestrous standardbred mares. Seventeen mares were selected for use in this experiment, on the basis of a previous normal reproductive history, and were housed under a photoperiod of 8L:16D beginning one week prior to the start of the experiment (second week in January). Mares were infused with 20 micrograms (n = 7) or 2 micrograms (n = 6) GnRH/h, or were subjected to photoperiod treatment only (controls, n = 4). Serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and progesterone did not vary, and neither significant follicular development nor ovulation was observed in any control mare throughout the experimental period (greater than 60 days). By contrast, both groups of GnRH-treated mares showed elevated serum concentrations of LH and FSH within one day after the start of infusion. Mares infused with 20 micrograms GnRH/h had at least one follicle greater than or equal to 25 mm in 7.4 +/- 1.3 (mean +/- SEM) days following the start of infusion, and ovulated in 12.0 +/- 0.7 days. In the 2-microgram-GnRH/h treatment group, a 25-mm follicle was detected in 5.7 +/- 0.7 days, and ovulation occurred after 10.0 +/- 0.3 days of infusion. Ovulation in every instance was followed by a functional luteal phase, as indicated by the profiles of progesterone secretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pulsatile administration of gonadotropin-releasing hormone advances ovulation in cycling mares

Cycling standardbred mares were infused with saline or 20 micrograms gonadotropin-releasing hormone (GnRH) in a pulsatile pattern (one 5-sec pulse/h, 2 h or 4 h) beginning on Day 16 of the estrous cycle. Although serum concentrations of luteinizing hormone (LH) increased significantly earlier in all three GnRH-treated groups (within one day of the initiation of infusion) compared to saline-infused controls, there were no differences in peak periovulatory LH concentrations among treatments (overall mean +/- SEM, 8.98 +/- 0.55 ng/ml). The number of days from the start of treatment to ovulation was significantly less in mares infused with 20 micrograms GnRH/h (mean +/- SEM, 2.9 +/- 0.6 days after the initiation of treatment, or 18.9 days from the previous ovulation; N = 7) compared to mares treated with saline (5.9 +/- 0.3 days, or 21.9 days from previous ovulation; N = 7) or 20 micrograms GnRH per 4 h (5.4 +/- 0.9 days or 21.4 days from previous ovulation; N = 5). Although mares infused with 20 micrograms GnRH/2 h ovulated after 4.3 +/- 0.7 days of treatment (Day 20.3; N = 7), this was not significantly different from either the control or 20 micrograms GnRH/h treatment groups. Neither the duration of the resulting luteal phase nor the length of the estrous cycle was different between any of the treatment groups (combined means, 14.7 +/- 0.2 days and 21.3 +/- 0.4 days, respectively). We conclude that pulsatile infusion of GnRH is effective in advancing the time of ovulation in cycling mares, but that the frequency of pulse infusion is a critical variable.     

Effective suppression of ovarian cyclicity in the lowland gorilla with an oral contraceptive

To determine the effects of a human oral contraceptive on normal and abnormal reproductive endocrine patterns in two lowland gorillas (Gorilla gorilla), daily urine samples were analyzed by radioimmunoassay for estrone conjugates (EC) and pregnanediol-3-glucuronide (PdG). During a pre-treatment period one female (F1) demonstrated regular menstrual cycles averaging 27.6 ± 1.8 days, whereas ovarian cyclicity in female 2 (F2) was consistently prolonged, ranging from 37–51 days. A 56 day regimen of an oral contraceptive (Demulen 50®) was administered to both females beginning in the late luteal phase, and within 6 and 7 days of treatment onset (F1 and F2, respectively) urinary EC and PdG declined to and remained at concentrations consistent with amenorrhea throughout the administration period. Ten and twenty days after contraceptive withdrawal (F1 and F2, respectively) an EC peak was observed with subsequent PdG elevations 1–2 days later. Mean cycle length and luteal phase durations were not different (P > 0.05) before or after treatment for either female, while combined peak PdG concentrations were greater (P < 0.05) for the first 3 months after treatment compared to pre-treatment values. These results indicate that a human oral contraceptive rapidly suppresses ovarian activity in female lowland gorillas, but that the abnormal endocrine pattern observed in F2 could not be redirected into a normal profile after contraceptive withdrawal. © 1992 Wiley-Liss Inc.     

Effect of changes in FSH induced by bovine follicular fluid and FSH infusion in the preovulatory phase on subsequent ovulation rate and corpus luteum function in the ewe

Treatment of Damline ewes with i.v. injections of various doses (2, 5 or 10 ml) of bovine follicular fluid for 72 h after prostaglandin-induced luteal regression resulted in a significant decrease in plasma concentrations of FSH after a 1.5-2 h delay but did not affect LH. The half life of this decrease in plasma FSH levels (156 min) after injection of follicular fluid was similar to that for clearance (159 min) of ovine FSH after infusion. A significant rebound increase in plasma FSH levels occurred by 13 h after all follicular fluid injections, and the magnitude of this rebound was inversely related to the dose of follicular fluid injected. A significant delay in the onset of oestrus occurred only with 5 and 10 ml bovine follicular fluid. There was no significant effect on ovulation rate or subsequent corpus luteum function as measured by plasma concentrations of progesterone. Infusion of ovine FSH (50 micrograms/h for 48 h) during the period of follicular fluid treatment prevented the delay in onset of oestrus and resulted in a substantial (2-10-fold) increase in ovulation rate. Corpus luteum function in terms of progesterone secretion was also enhanced. These results show that (1) intermittent suppression of FSH during the preovulatory period in the ewe does not affect subsequent ovulation rate or corpus luteum function and (2) the delay in the onset of oestrus induced by bovine follicular fluid can be prevented by exogenous FSH.     

Transvaginal, ultrasound-guided biopsy of the corpus luteum in cattle

An ultrasound-guided transvaginal technique for corpus luteum biopsy was developed and tested in cattle. The biopsy needle set consisted of an inner needle (o.d. 1 mm) with a 20-mm long specimen notch, an outer cannula (o.d. 1.2 mm) with a cutting edge, and an automated spring-loaded handle with trigger. The biopsy needle set was inserted into the channel guide of the handle of a convex-array transvaginal ultrasound probe. The transducer was positioned in the vaginal fornix, and the ovary was manipulated transrectally against the vaginal wall and transducer face. During monitoring on the ultrasound screen, the inner needle was pushed through the vaginal wall into the corpus luteum, and the cutting cannula was fired, cutting and trapping luteal tissue in the specimen notch. Three luteal biopsies at each of Hours 0 and 4 were taken 10 d after ovulation in 6 heifers; 6 other heifers served as controls. A biopsy core was obtained in 36 of 39 attempts (92%). The tissue specimens seemed normal based on gross evaluation. The effect of biopsy on luteal function was assessed by daily ultrasound monitoring of luteal area, by assay of progesterone concentrations in blood samples obtained daily, and by the length of the interval from biopsy to ovulation. No significant differences were found for post-biopsy function for any of the 3 end points. The results indicated repeated transvaginal, ultrasound-guided biopsy of the corpus luteum in cattle is a practical procedure and may be useful for experimental and diagnostic purposes.     

Determination of the time of ovulation in chimpanzees by measurement of LH, estrone sulfate, and pregnanediol 3 alpha-glucuronide in urine: comparison with serum hormone patterns.

The concentrations of LH, total estrogens, and pregnanediol 3 alpha-glucuronide (PdG) were determined by specific radioimmunoassays on daily overnight urine samples obtained in 13 menstrual cycles of six adult female chimpanzees during the periods of increasing, maximal, and decreasing tumescence of the perineal sex skin. The peaks of estrogens and LH and the rise in PdG in urine accurately reflected the peaks of estradiol-17 beta and LH and the subsequent rise in progesterone in the serum of the same animals during the same menstrual cycles, and can be used to predict and verify the occurrence of ovulation, thus avoiding the repeated tranquilizations necessary to obtain daily blood samples.     

The ability of subordinate follicles of the second follicular wave to become dominant is lost by day 15 of the estrous cycle in cattle

Generally, unilateral ovariectomy before a critical period in the latter part of the estrous cycle induces a transitory increase in plasma FSH, which causes subordinate follicles to develop and maintain ovulation rates characteristic of the species. A limiting period for subordinate follicles to assume dominance and from which ovulation occurs has not been shown for cattle. Growth and/or regression of subordinate follicles were characterized following removal of the dominant follicle at different days of the luteal phase of the estrous cycle in cattle in this study. In the mid-luteal phase (Day 13 or 15), the ovary with the dominant follicle of the second wave was ablated via unilateral ovariectomy; the corpus luteum also was removed. In the late luteal phase (Day 17 or 19), the dominant follicle was ablated with an ultrasonically guided 20 gauge needle. When the dominant follicle was removed on Day 13, the largest subordinate follicle of the second wave of follicular development became dominant and ovulation occurred from this follicle in 4 of 4 animals. However, when the dominant follicle was removed on Day 15, 17 or 19, a new wave of follicular development was induced in 14 of 15 animals. Moreover, the recovered subordinate follicle of the second wave of follicular development had similar growth characteristics to naturally occurring dominant follicles. In conclusion, the subordinate follicle in the second follicular wave in cattle retained the ability to become dominant, but this ability was lost by Day 15 of the estrous cycle. However, cattle then were able to maintain ovulation by developing a new wave of follicular growth.     

Estrus induction in white rhinoceros (Ceratotherium simum)

The estrous cycle length in the white rhinoceros (Ceratotherium simum) is either 4 or 10 wk. The cause(s) for this variation as well as the poor fertility rate in captivity remains under debate in this species. Most captive adult white rhinoceros undergo long anovulatory periods without luteal activity which are considered a major reason for their low reproductive rate. In this study, the synthetic progestin chlormadinone acetate (CMA) was tested in combination with hCG or the GnRH analogue deslorelin for its efficiency to induce ovulation in fourteen females without luteal activity and in three, regular cycling females. HCG (N = 12), injectable GnRH analogue (N = 8) and GnRH analogue implants (N = 15) were given to induce ovulation after CMA treatment. Treatment success was determined using both transrectal ultrasonography and progesterone metabolite EIA analysis. A preovulatory sized follicle (3.5 ± 0.1 cm) or a corpus luteum (5.1 ± 0.7) was present on the ovary one day after induction in 93.1% of the treatments. Despite this high rate of ovarian response, ovulation rate differed between the study groups. The ovulation rate for hCG, injectable GnRH analogue and GnRH analogue implants was 66.7%, 62.5% and 93.3%, respectively. Ovulation rate in cyclic females treated with GnRH implants was 100% (6/6) compared with 89% (8/9) in females without luteal activity receiving the same treatment. The length of the estrous cycle when induced with hCG was 4 wk (85.7%). The estrous cycle when induced with GnRH analogue was predominantly 10 wk long. Two females without luteal activity treated with GnRH became pregnant. In conclusion, CMA in combination with GnRH analogue implants was highly effective to induce ovulation in white rhinoceroses and thus can contribute to efforts aimed at increasing natural mating and reproductive rates in the captive white rhinoceros population.     

Pregnancy and ovulation detection in bison (Bison bison) assessed by means of urinary and fecal steroids.

Sexually mature bison (Bison bison) cows were tested for both pregnancy and ovulation by means of urinary steroid metabolites and fecal steroids. The accuracy of pregnancy diagnosis was determined among 18 bison cows, in approximately the third month of gestation, by means of urinary pregnanediol-3 delta-glucuronide (PdG), urinary estrone conjugates (E1C), and fecal total estrogens (TE). Urinary PdG was 100% accurate, urinary E1C was 89% accurate, and fecal TE was 100% accurate in predicting pregnancy. Fecal progesterone (P4) and TE, as well as urinary E1C and PdG concentrations all increased from conception (August) through January, but significant differences were not apparent until November. During the rutting season ovulation was detected by increases in either urinary PdG or fecal P4 concentrations. Both pregnancy and ovulation were detected in uncaptured bison with reasonable accuracy by means of urinary and fecal steroids or their metabolites.