In a survey of gynecologic lesions in female zoo felids conducted to determine if the widely used progestin contraceptive melengestrol acetate (MGA) had adverse effects, numerous leiomyomas and leiomyosarcomas were detected. This current study aimed to characterize the morphologic features of these tumors, determine their prevalence, and assess if MGA was a risk factor for their genesis. Genital tracts from 219 zoo felids representing 23 species were evaluated, and leiomyomas were detected in 24% of the felids. Leiomyomas were often multiple and occurred in the myometrium, ovary, or adjacent broad ligament. The risk of developing leiomyomas increased with age, but MGA treatment or parity had no effect. Five other felids had leiomyosarcomas. Leiomyosarcomas were distinguished from poorly demarcated leiomyomas by the presence of local invasion, metastasis, and cellular atypia, but necrosis and mitotic rate were not distinguishing criteria. Four of five felids with leiomyosarcomas had been treated with MGA. These results indicate that leiomyomas are common spontaneous lesions in the genital tracts of zoo felids and their genesis is not linked to MGA exposure. Whether progression to malignancy is promoted by MGA warrants further investigation.

To determine the onset of breeding season and to monitor endocrine events during successive ovarian cycles, blood samples were drawn from three adult female Rocky Mountain goats (Oreamnos americanus) three times weekly for 2 mo in the autumn of 1989 and 1990. Serum estradiol and progesterone concentrations measured by radioimmunoassay indicated that ovarian activity began in November. The first progesterone increase of the season was attenuated and transient, suggesting insufficient corpus luteum development. Luteal phases of subsequent cycles were typical in both amplitude and length of those in other ruminant species. Cycle length ranged from 21 to 33 days, whereas luteal phases ranged from 13 to 17 days (two females, two cycles each). Progesterone remained elevated for at least 6 mo in the third female, perhaps associated with pseudopregnancy.

The release of hypothalamic-pituitary-adrenocortical hormones was studied in intact and neutered gray wolves (Canis lupus) to determine how these hormones interact and affect reproductive hormones. Experiments were performed on adult wolves anesthetized with 400 mg ketamine and 50 mg promazine. Intravenous (i.v.) injections with 50 micrograms ovine corticotropin releasing factor (oCRF) significantly increased adrenocorticotropin (ACTH; P < or = 0.01), cortisol (CORT; P < or = 0.004), and progesterone (P < or = 0.036), but not beta-endorphin (P > or = 0.52). Since neutered wolves demonstrated dose-dependent elevations in response to ACTH, it was concluded that the progesterone was secreted from the adrenal gland. Basal luteinizing hormone (LH) concentrations in neutered wolves were similar before and 60 min after i.v. injection of 1, 5, or 25 IU ACTH (P > or = 0.36) or 2.2 mg/kg cortisol (P = 0.42). Neither 25 IU ACTH (P = 0.55) nor 0.22 mg/kg dexamethasone (P = 0.49) altered the LH response to injection of LH releasing hormone in neutered wolves. Chronic administration of 0.22 mg/kg/day dexamethasone for 3 d did not alter baseline LH concentrations (P = 0.75). Injection of 1.0 mg/kg naloxone (NAL), however, increased LH concentrations relative to baseline values in both intact (P = 0.032) and neutered (P = 0.0005) female wolves, but not in intact (P = 0.19) or neutered males (P = 0.07). These results indicated that in gray wolves (1) oCRF stimulated the release of pituitary and adrenal hormones in a fashion similar to that of other mammals; (2) the adrenal cortex was capable of secreting progesterone into the systemic circulation; (3) exogenous glucocorticoids did not alter LH concentrations; and (4) endogenous opioids may modulate LH secretion in female wolves.

The U.S. Congress protected feral on western rangelands and delegated responsibility for their management to the Bureau of Land Management (BLM) and the U.S. Forest Service with the passage of the Wild Freeroaming Horse and Burro Act of 1971. Of the 39,000 feral on public rangelands in the western United States in 1988, about 38,000 occupied lands administered by BLM, and >27,000 of these were in Nevada (U.S. Bur. Land Manage. 1990:19-20). Thus, BLM's Nevada state office is responsible for the management of about 70% of all wild free-roaming in the United States. Since protection was initiated in 1971, feral horse populations have grown. Estimates of the rates of increase of individual populations range from 8-30%/year (Natl. Res. Council 1980:55, Wolfe 1980). Garrott et al. (1991b) examined fecundity and survival estimates available in the literature and BLM records of horse populations with preand postcapture counts. The estimated growth rates of 12 populations ranged from 15-27%/year, with an unweighted mean of 21%. The passage of the Public Rangelands Improvement Act of 1978 (PRIA) reflected concern that the quality of western rangelands was being degraded and directed BLM to remove excess feral that pose a threat to their habitat. BLM conducted periodic roundups to reduce horse numbers on western rangelands to an arbitrarily stated appropriate management level for each herd area, which supposedly reflects feral horse numbers in 1971. Excess horses were disposed of through the Adopt-a-Horse program. This program has been controversial and expensive. Opposing viewpoints are held by organizations interested in preservation of feral and by livestock interests. BLM placed 9,500 through adoptions at a cost of $3.5 million in fiscal year 1985, but 10,000 were not adopted and were maintained in corrals, costing $6 million that fiscal year (Boyles 1986). Because the control of feral horse populations through roundups was deemed an unacceptable long-term solution to this management problem, the National Academy of Sciences Committee on Wild and Free-roaming Horses and Burros recommended that the feasibility of using contraception be studied (Natl. Res. Council 1980:218-220, 1982). We began a project in September 1985 to develop chemical contraception in feral mares (Plotka et al. 1988b, Plotka et al. 1989, Plotka et al. 1992) and to test the efficacy of such a treatment in field conditions. We report the results of the field tests of feral mare contraception and discuss the applicability of these results to managers.

Vaginal cytology was used to monitor ovarian cycles, two pregnancies, and three pseudopregnancies. Vaginal smears were collected two or three times per week from three adult females; smears plus blood samples were collected once per week from a fourth, adolescent female. Mean cycle lengths, based on intervals between onset of leukocyte infusions, were 11.9 +/- 4.9 days (n = 43 cycles), 10.8 +/- 5.1 days (n = 49), and 12.3 +/- 6.3 days (n = 7) for the three females. Weekly hormone data from the adolescent female revealed a correlation between serum estradiol and percent anuclear cells, suggesting that these cells may be indicative of estrus. The fourth female experienced two sustained, 6-week increases in serum progesterone, one spontaneous and the other following follicle-stimulating hormone (FSH) administration. Leukocyte infusions continued during these periods of increased progesterone secretion. However, leukocyte infusions ceased during the two pregnancies of one adult female and during two FSH-induced pseudopregnancies of another.

Homogeneous Silastic® rods containing ethinylestradiol (EE) (1.5 or 4 g), estradiol-17β (E) (4 g) or progesterone (P) (6 g) were implanted into feral mares (Equus caballus) between 4-and 10-yr-old. Six treatment groups (≥10 mares/group) of non-pregnant mares received 36 g P and 12 g E (P + E), 36 g P and 8 g EE (P+HEE), 1.5 g EE (LEE), 3 g EE (MEE), 8 g EE (HEE) or control-implanted mares (CI). CI received implants containing no steroid. Two groups of pregnant mares received P + HEE or HEE. Stallions were placed with the mares 15 to 26 mo after implanting. Blood was collected biweekly for up to 28 mo after implanting and serum analyzed for P by radioimmunoassay. A single P value ≥2.5 ng/ml indicated ovulation and 2 consecutive values ≥2.5 ng/ml indicated pregnancy. Serum from blood collected before and at 4, 12, 24, 50, 64 and 89 wk after implanting was analyzed for EE concentrations. All animals pregnant at the time of contraceptive placement delivered normal foals. Contraceptive efficacy for groups LEE, MEE, HEE and P + HEE were 75, 75, 100, and 100%, respectively after two breeding seasons. Suppression of ovulation appeared to be inversely related to the concentration of EE used in the implant. The percent of animals ovulating after 2 yr of contraception in each group was 100, 100, 88, 62, 20, and 12 for groups CI, P+E, LEE, MEE, HEE and P+HEE, respectively. The pregnancy rate for the same groups was 100, 78, 25, 25, 0 and 0%, respectively. Contraceptive efficacy was followed for 3 yr in one group, P + HEE, and was 88%. Pregnancy rates for groups P+E and CI after 3 yr was 78 and 82%, respectively. Our data demonstrate effective contraception of feral mares for up to 36 mo without compromising a pregnancy in effect at the time of implanting. Calculating the decline in EE concentrations to 150% of pre-implantation concentrations, these data suggest an effective contraceptive life of approximately 16, 26, and 48 to 60 mo for LEE, MEE and HEE implants, respectively. Mechanisms that appear to be involved in contraceptive efficacy include preventing ovulation at higher concentrations of steroids and either suppressing ovulation or implantation at lower concentrations of steroid.

From 1980 to 1989, experiments were conducted on 28 intact (13 females, 15 males) and 10 neutered wolves (5 females, 5 males) to characterize prolactin (PRL) release. From these studies, we have (i) adapted and validated the canine PRL radioimmunoassay of Parlow for wolves; (ii) determined that the plasma half-life of PRL is 44 min; (iii) demonstrated that anesthesia with 400 mg ketamine plus 50 mg promazine, 400 mg ketamine plus 30 mg xylazine, or 7.5 μg∙kg−1 etorphine plus 0.5 mg∙kg−1 xylazine, administered intramuscularly, does not alter PRL rhythms or control mechanisms; (iv) indicated that PRL is not secreted in response to handling stress (P ≥ 0.78) or by activation of the hypothalamic–pituitary–adrenocortical axis simulated by intravenous injection of 50 μg ovine corticotropin-releasing factor (P = 0.28); (v) demonstrated a circannual rhythm in intact and neutered wolves characterized by elevated PRL levels just prior to summer solstice; (vi) detected a circadian PRL rhythm in females; (vii) provided evidence for dopaminergic control of PRL secretion by injecting 2.0 mg∙kg−1 promazine, a dopaminergic antagonist, which increased PRL levels significantly (P = 0.0001); (viii) shown that intravenous injection of 100 μg thyrotropin-releasing hormone results in PRL release (P = 0.0001), but that this release could not be attenuated by prior administration of 1.0 mg∙kg−1 of the opioid antagonist naloxone; (ix) determined that feeding 2.0 mg of melatonin daily reduced basal PRL levels in May and June (P = 0.03), but not in October–December (P = 0.42), and that PRL stimulation with 100 μg thyrotropin-releasing hormone was consistently lower in melatonin-fed wolves; and (x) shown that pinealectomy does not abolish the circadian PRL rhythm nor alter absolute PRL levels relative to sham-operated control wolves (P = 0.33).

The feasibility of using transrectal ultrasonography for imaging the in situ morphology of the reproductive tract of females of several large nondomestic and endangered species was studied. Two black (Diceros bicornis) and 1 white (Diceros simus) rhinoceros, 2 Asian (Elaphus maximus) and 2 African (Loxodonta africana) elephants, 4 banteng (Bos javanicus), 1 gaur (Bos taurus), 1 giraffe (Giraffa camelopardalis), and 1 bactrian camel (Camelus bactrianus) were examined. Real-time ultrasonic images were obtained for the following structures: 1) rhinoceros-corpus luteum, ovarian follicles, uterus, cervix, and early conceptus, 2) elephants-posterior uterus and cervix, 3) banteng and gaur-corpus luteum, ovarian follicles, uterus, cervix, and conceptus, 4) giraffe-posterior uterus, placentomes, and late conceptus, 5) camel-posterior uterus, fetal fluids, and fetal membranes. Individual ovarian follicles were identified and monitored over a 34 day observational period in 1 nontranquilized white rhinoceros. Difficulties and limitations in viewing the ovaries in the elephants were attributed to operator inexperience and to the size, positioning, and demeanor of the animals. Pregnancy was detected in 1 black rhinoceros (27 days), 1 banteng cow (48 days), the giraffe (13 months), and in the bactrian camel (approximately 3 1/2 months). Impending embryonic loss was suspected in the banteng cow because a heartbeat was not detected in the embryo proper; the cow was subsequently diagnosed nonpregnant by transrectal palpation 20 days later. It is concluded that the ability afforded by transrectal ultrasonography to detect and measure ovarian structures and changes in morphology of the tubular genitalia and conceptus provides a research methodology for the elucidation of certain aspects of reproductive biology, and a clinical modality for reproductive management and assisted fertilization programs of large nondomestic species.

Two age-specific reproduction schedules were constructed for feral horses (Equus caballus) on the basis of lactation status of 14 788 females captured during herd reduction programs and pregnancy rates of 667 horses determined by serum progesterone assays. The probability of detecting lactation progressively decreased for females captured further from the foaling season, indicating that these data resulted in substantial underestimates of true foaling rates. A third reproductive schedule was, therefore, constructed on the basis of a subsample of 1144 horses captured immediately after the foaling season in June. Characteristics common across all three data sets were first reproduction at age 2, an increase in the proportion of females foaling through age 6, highest foaling rates from 6 to 15 years, and a gradual decrease in foaling rates of females >15 years. Variability in the proportion of reproductively active females in each age-class was detected among populations and among years within a population; however, the general trend was high reproductive rates, with 80–90% of the prime-age females foaling. The reproduction model suggested by L. L. Eberhardt, provided a close mathematical approximation of the observed age-specific changes in foaling rates, providing a useful tool for the construction of reproduction schedules required for age-structured population models.

Although serum hormones varied seasonally in all adult animals, only dominant male and female wolves urine-marked. Serum testosterone and urine-marking rates, which increased during the fall/winter breeding season, were positively correlated in both male and female dominant wolves. Estradiol, which increased in conjunction with proestrus and estrus, was not correlated with female urinemarking. These findings suggest that hormonal influence on urine-marking in the wolf is modulated by social factors and contrast with those for both domestic dogs and coyotes, two other members of the genus Canis.

Silastic rods containing either melengestrol acetate (MGA) or levonorgestrel (LN) were placed in anestrous white-tailed deer (Odocoileus virginianus borealis) does to evaluate the contraceptive efficacy of the implants over a 2 yr period. Implants of MGA were placed in five does during mid-pregnancy to evaluate the effect of this treatment on pregnancy, parturition and lactation. Pregnancies were not observed in the five animals implanted with MGA during anestrus. Three of five does implanted with LN became pregnant in the first season. Pregnancy was not interrupted in the five pregnant does implanted with MGA and it was necessary to remove the implants and treat the does with an estrogen to achieve parturition. One of five fawns was delivered alive and was raised by the doe. MGA was effective for 2 yr as a contraceptive in white-tailed deer, LN was ineffective as used, and MGA placed in pregnant does delayed or prevented normal parturition and thus should not be used in pregnant deer.

Rat uterine estrogen receptors (ER) and progesterone receptors (PR) have been used as controls in ER and PR assays of breast tumors. Stunning or decapitation of experimental animals without prior anesthesia is no longer acceptable as a method of killing. Thus, we compared the effects of two anesthetics on the concentration of rat uterine ER and PR. Rats were killed by one of three methods: (a) stunning, (b) ether anesthesia followed by decapitation, or (c) ketamine anesthesia followed by decapitation. ER and PR concentrations were determined by titration assay, with dextran-coated charcoal separation, and quantified by Scatchard analysis. No significant differences were found in mean receptor concentrations or dissociation constants for the three groups. The results indicate that there is no residual effect of diethyl ether or ketamine hydrochloride on the binding of either estrogen or progestin to their respective receptors. The use of decapitation after either ether or ketamine anesthesia is appropriate for measuring ER and PR receptors in rat uteri.

Ovarian function was monitored for 33 mo in captive feral mares (Equus caballus) by following serum progesterone (P) levels. A P level greater than 2.0 ng/ml was considered indicative of ovulation. Feral mares were seasonally polyestrus with the majority of animals ovulating between May and October. During the first year after capture, none of the mares ovulated during the anestrous season. However, in subsequent years, approximately 10% of mares ovulated during the months of November, January and February. P levels during the luteal phase of the cycle ranged from 2.0 to 21.0 ng/ml which were similar to levels in domestic breeds of mares. The pattern of P concentrations during pregnancy was also similar to the pattern in domestic mares. These data confirmed the seasonality of ovulation in feral mares but indicated that this seasonality was not as rigid as previously believed. Captive feral mares were similar to domestic breeds in the percentage of mares ovulating all year and in the P levels achieved during the estrous cycle and pregnancy.

Blood was collected from 486 feral horses of mixed sex and age classes captured from three wild horse management areas in Nevada and Oregon from December 1985 to February 1986. Males were significantly outnumbered by females in the Flanigan area, but both sexes were represented in approximately equal numbers in the Wassuk and Beaty's Butte areas. Hematology and chemistry values averaged 16.4 +/- 0.11, 46.3 +/- 0.28, 9.9 +/- 0.07, 6.9 +/- 0.10, 47.1 +/- 0.24, 16.6 +/- 0.09, 35.2 +/- 0.09, 10.4 +/- 0.14 and 23.4 +/- 0.25 for hemoglobin (HGB), hematocrit (HCT), red blood cells (RBC), white blood cells (WBC), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), cortisol (F) and serum urea nitrogen (SUN), respectively. Statistically significant differences in HGB, HCT, RBC, WBC, MCV and MCH levels occurred with respect to age (P less than or equal to 0.001). Serum F levels were lower in immature animals than in either subadult or adults in all areas. Flanigan horses appeared in the poorest condition and had the lowest HGB, HCT and RBC counts while the values for Wassuk horses were significantly higher (P less than or equal to 0.001). Serum F levels were lowest in the Flanigan horses. A significantly lower (P less than or equal to 0.001) proportion of adult mares had progesterone levels consistent with pregnancy in the Flanigan horses versus those from the other two areas. These data are consistent with a subjective evaluation of the condition of the horses.

Serum samples were collected weekly for 3 yr from two female African elephants, for 18 mo from two other female African elephants, and for 2 yr from two female Asian elephants. Animals were not sedated at the time of blood collection. Ovarian cycles, characterized by changes in progesterone and immunoreactive luteinizing hormone (ILH) concentrations, averaged 15.9 +/- 0.6 wk (N = 25) for African females and 14.7 +/- 0.5 wk for Asian females (N = 10). The length of the active luteal phase averaged 10.0 +/- 0.3 wk for African elephants (range 8-14 wk) and 10.6 +/- 0.6 wk for Asian females (range 9-13 wk). Interluteal phases were 5.9 +/- 0.6 wk for African females and 4.2 +/- 0.5 wk for Asian females. One African female (Maliaca) had two extended interluteal phases, both occurring between the months of February and May. Excluding these two periods, there were no differences in the length of the ovarian cycle or the length of the luteal phase between species of elephant. Serum progesterone in both species ranged from less than 50 pg/ml to 933 pg/ml. Average progesterone concentrations during the luteal phase were significantly lower in African elephants compared with Asian elephants (328 +/- 13, N = 30 cycles vs. 456 +/- 23, N = 14 cycles; p less than 0.001). ILH ranged from nondetectable to 11.6 ng/ml. These data suggest that the length of the ovarian cycle in the African elephant is about 16 wk and confirm that the length of the ovarian cycle in the Asian elephant is about 15 wk.

Five groups of 30 captive feral mares each were implanted with silastic rods containing estradiol (E) and/or progesterone (P): E only with 8 g, P only with 24 g, P+HE with 8 g P + 8 g E, HP+E with 12 g P + 4 g E, HP+LE with 12 g P + 2 g E. Arbitrary group designations were differentiated by relative high (H) and low (L) amounts of steroid. Thirty mares received silastic rods containing no hormone (CI). Five mares from each group were bled every 2 wk for 4 mo and monthly for another 5 mo. All mares were tested for estrus by allowing them to stand in an alley between two pens of stallions and visually monitoring her response to the stallion. Serum P levels increased from 0.3 +/- 0.1 to 1.8 +/- 0.1 ng/ml in the P only group during the first 3 wk after implanting. Levels remained stable for the next 2 wk and then began a gradual decline. Serum P levels in the other groups were lower. Serum E levels were slightly increased in the groups receiving 8 g of E (E only and P+HE groups). Significantly fewer animals in the E only and P+HE groups exhibited estrus as compared with control animals (10 of 23 and 13 of 26 versus 22 of 25, respectively, P less than or equal to 0.003). However, animals receiving 24 g of P (P only) showed similar occurrences of estrus as controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Forty-eight newly captured free-ranging feral stallions (Equus caballus) from two different locations and six captive stallions were immobilized using combinations of etorphine hydrochloride, xylazine hydrochloride and atropine sulfate with or without acepromazine. Six animals were immobilized twice, 1 mo apart. The drugs were administered either intramuscularly (n = 13) or intravenously (n = 44). Mean immobilization time (+/- SE) after intravenous (i.v.) injection of etorphine, xylazine and atropine was 55 +/- 4 sec (range 20 to 185 sec) compared to 708 +/- 131 sec (range 390 to 1,140 sec) for intramuscular (i.m.) injection. Immobilization was reversed with i.v. administration of 3 to 11 mg diprenorphine hydrochloride and 16 to 24 mg yohimbine hydrochloride. Average time from administration to standing and walking was 86 +/- 7 sec (n = 55). Reversal of etorphine-induced immobilization with an amount of diprenorphine equal to the etorphine and administered i.v. was as effective as a 2:1 ratio of diprenorphine to etorphine. Acepromazine had no effect on induction time, but decreased relaxation after immobilization and prolonged ataxia after reversal of the etorphine and xylazine. Eight free-ranging horses were immobilized in 708 +/- 132 sec by darting with 5.5 mg etorphine, 1,300 mg xylazine and 15 mg atropine from a helicopter. Three animals died during the study: one immediately after reversal of an i.v. administration, one from a broken neck during induction from darting, and one was found a week later at the site of darting.(ABSTRACT TRUNCATED AT 250 WORDS)