Mating-induced luteinizing hormone surge and ovulation in the female camel (Camelus dromedarius)

Blood samples were collected after mating from four female one-humped camels every 10 min for 9-12 h. Luteinizing hormone (LH) was quantified in plasma by radioimmunoassay using antibovine LH. Of the seven observed matings, five were followed by a release of LH, and three by an ovulation (indicated by a subsequent secretion of progesterone). LH levels at the time of mating ranged from 0.7 to 3 ng/ml. When an LH response occurred, the levels increased 1 h after mating and reached a maximum in 2-3 h (ranging from 2.9 to 19.1 ng/ml). A decrease in LH was observed starting 6 h after mating and lasting for 6 h. These results are in agreement with a coitus-induced mechanism of ovulation in the one-humped camel (Camelus dromedarius). They confirm and extend the observations reported in the bactrian camel (Camelus bactrianus).     

Changes in plasma estradiol, progesterone and LH level in the menstrual cycle of the adult female Japanese monkey during the mating season

Adult 15 female Japanese monkeys showing regular menstrual cycles were subjected to the daily blood sampling for the measurement of estradiol (E2), progesterone (P) and biological LH in the mating season. Monkeys were maintained under controlled conditions in a standardized environment. Of the 35 cycles observed, 18 (51.4%) were estimated as anovulatory cycles and 17 (48.6%) were ovulatory cycles. The anovulatory cycles were classified into three types according to the peak level of E2 (Type I: E2 less than 50 pg/ml 3 cycles, Type II: E2 less than 170 pg/ml 7 cycles, Type III: E2 greater than 170 pg/ml 8 cycles). The ovulatory cycles were classified into two Types according to the peak level of P (Type IV: P less than 5.0 ng/ml 5 cycles, Tyep V: P greater than 5.0 ng/ml 12 cycles). The menstrual cycle was 27.5 +/- 7.8 days. The differences between mid cycle LH surge and P level in Type IV and in Type V were statistically significant. It was revealed that female Japanese monkeys kept under controlled condition in the mating season showed high incidence of various types of anovulatory cycles and that the ovulatory cycles with low P elevation in the mid luteal phase showed low LH and P secretions on the mid cycle date.     

Characterization of the oestrous cycle and mating season of squirrel monkeys from copulatory behaviour.

Observations of the behaviour of squirrel monkeys, including 8 opposite-sex pairs during daily 30-min social encounters and 2 mixed-sex permanent groups during daily 30-min observation sessions, over a 14-month period were used to determine the periodicity of the oestrous cycle and annual mating season. The median and modal length of the oestrous cycle was 8 days, within which copulations were limited to a 1--2 day period. In a cyclic female, plasma progesterone levels over a 24-day period dropped from 85--151 ng/ml to 25 ng/ml 2 days before oestrus. In non-cyclic females plasma progesterone values were less than 15-4 ng/ml. Males exhibited a 6-8--19-7 week 'season' of copulation and ejaculation. The onset of this 'mating season' in August coincided with the annual peak in male body weight (the 'fatted male' phenomenon).     

Effects of lactational and reproductive status on ovarian follicular waves in llamas (Lama glama)

The effects of lactational status and reproductive status on patterns of follicle growth and regression were studied in 41 llamas. Animals were examined daily by transrectal ultrasonography for at least 30 days. The presence or absence of a corpus luteum and the diameter of the largest and second largest follicle in each ovary were recorded. Llamas were categorized as lactating (N = 16) or non-lactating (N = 25) and randomly allotted to the following groups (reproductive status): (1) unmated (anovulatory group, N = 14), (2) mated by a vasectomized male (ovulatory non-pregnant group, N = 12), (3) mated by an intact male and confirmed pregnant (pregnant group, N = 15). Ovulation occurred on the 2nd day after mating with a vasectomized or intact male in 26/27 (96%) ovulating llamas. Interval from mating to ovulation (2.0 +/- 0.1 days) and growth rate of the preovulatory follicle (0.8 +/- 0.2 mm/day) were not affected by lactational status or the type of mating (vasectomized vs intact male). Waves of follicular activity were indicated by periodic increases in the number of follicles detected and an associated emergence of a dominant follicle that grew to greater than or equal to 7 mm. There was an inverse relationship (r = -0.2; P = 0.002) between the number of follicles detected and the diameter of the largest follicle. Successive dominant follicles emerged at intervals of 19.8 +/- 0.7 days in unmated and vasectomy-mated llamas and 14.8 +/- 0.6 days in pregnant llamas (P = 0.001). Lactation was associated with an interwave interval that was shortened by 2.5 +/- 0.05 days averaged over all groups (P = 0.03). Maximum diameter of anovulatory dominant follicles ranged from 9 to 16 mm and was greater (P less than 0.05) for non-pregnant llamas (anovulatory group, 12.1 +/- 0.4 mm; ovulatory group, 11.5 +/- 0.2 mm) than for pregnant llamas (9.7 +/- 0.2 mm). In addition, lactation was associated with smaller (P less than 0.05) maximum diameter of dominant follicles averaged over all reproductive statuses (10.4 +/- 0.2 vs 11.7 +/- 0.3 mm). The corpus luteum was maintained for a mean of 10 days after ovulation in non-pregnant llamas and to the end of the observational period in pregnant llamas. The presence (ovulatory non-pregnant group) and persistence (pregnant group) of a corpus luteum was associated with a depression in the number of follicles detected and reduced prominence of dominant follicles (anovulatory group greater than ovulatory non-pregnant group greater than pregnant group).(ABSTRACT TRUNCATED AT 400 WORDS)     

Endocrine changes during pregnancy, parturition and the early post-partum period in the llama (Lama glama)

Mean (+/- s.d.) pregnancy length for the 14 llamas in this study was 350 +/- 4.5 days. Plasma progesterone concentrations increased by 5 days after mating and remained elevated (greater than 2.0 ng/ml) throughout most of pregnancy. At about 2 weeks before parturition, plasma progesterone concentrations began to decline, dropped markedly during the final 24 h before parturition, and returned to basal concentrations (less than 0.5 ng/ml) by the day of parturition. The combined oestrone + oestradiol-17 beta and oestradiol-17 beta concentrations varied between 6 and 274 pg/ml and 4 and 114 pg/ml, respectively, during the first 9 months of pregnancy. Concentrations increased between 9 months after mating and the end of pregnancy with peak mean concentrations of 827 +/- 58 (s.e.m.) pg oestrone + oestradiol-17 beta/ml (range: 64-1658) and 196 +/- 10 pg oestradiol-17 beta/ml (31-294) during the last week of pregnancy. Concentrations then declined to 87 +/- 14 pg oestrone + oestradiol-17 beta/ml (7-488) and 25 +/- 5 pg oestradiol-17 beta/ml (2.5-142) during the first week post partum. Plasma cortisol concentrations varied between 2.6 and 51.9 ng/ml (14.0 +/- 0.5) from mating until 2 weeks before parturition when the concentrations began to decline. Only a slight increase in plasma cortisol concentrations was observed in association with parturition. Plasma triiodothyronine concentrations varied between 0.5 and 4.5 ng/ml (1.9 +/- 0.1) throughout pregnancy and the periparturient period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Progesterone and testosterone concentrations during oestrous cycle and pregnancy in the common vole (Microtus arvalis Pallas)

Serum progesterone and testosterone concentrations were measured during different stages of oestrous and pregnancy in paired and unpaired female common voles (Microtus arvalis). Hormone concentrations were measured by ELISA, and cycle stages were determined by vaginal smears. Paired females usually had serum progesterone concentrations of more than 10 ng/ml in the oestrous cycle. A significant maximum was detected in prooestrous (51.70 +/- 7.84 ng/ml, mean +/- S.D.). Serum progesterone concentrations increased from about 40 ng/ml at the beginning of pregnancy to about 70 ng/ml on days 15 and 16. The last 2 days before parturition (days 19 and 20) were characterised by a decrease of progesterone concentrations to ca. 30 ng/ml. The maximum concentration of testosterone was found in prooestrous (1.58 +/- 0.31 ng/ml). Concentrations during pregnancy varied between 1.5 and 2.1 ng/ml. In two of three cases unpaired females exhibited progesterone values below 10 ng/ml, but with varying vaginal smear patterns. The combination of progesterone concentrations and vaginal smear patterns was found to be regular in only 23.8% of the cases. The most frequent cycle stage found was the oestrous (44.2%). Mean concentrations of progesterone (10.43 +/- 13.81 ng/ml) and testosterone (0.85 +/- 1.11 ng/ml) in unpaired females were significantly lower than in paired females, thereby denoting reproductive inactivity in the former. The study presents basic data for several parameters of the reproductive biology in the common vole and confirms the importance of combining hormone assays and vaginal smear monitoring in reproductive research.     

Hormone concentrations before and after semen-induced ovulation in the bactrian camel (Camelus bactrianus)

During the follicular phase of bactrian camels, basal concentrations of LH were 2.7 +/- 1.2 ng/ml. By 4 h after insemination peak values of 6.9 +/- 1.0 ng/ml occurred. In addition, a smaller LH peak (5.4 +/- 2.5 ng/ml) appeared 1 day before regression of the follicle began in unmated camels. During the follicular phase peripheral plasma progesterone values were low (0.36 +/- 0.28 ng/ml), but values increased to reach 1.73 +/- 0.74 ng/ml at 3 days and 2.4 +/- 0.86 ng/ml at 7 days after ovulation. Plasma oestradiol-17 beta concentrations were 26.8 +/- 9.0 pg/ml during the follicular phase and 30.8 +/- 5.1 pg/ml when the follicle was maximum size. Values fell after ovulation but rose to 29.8 +/- 6.5 pg/ml 3 days later.     

Social suppression of ovarian cyclicity in captive and wild colonies of naked mole-rats, Heterocephalus glaber

To investigate the endocrine cause of reproductive suppression in nonbreeding female naked mole-rats, animals from 35 colonies were studied in captivity. Urinary and plasma progesterone concentrations were elevated in pregnant females (urine: 10.0-148.4 ng/mg Cr, 27 samples from 8 females; plasma: 3.6-30.0 ng/ml, 5 samples from 5 females; Days 21-40 of pregnancy) and cyclic breeding females (urine: 0.5-97.8 ng/mg Cr, 146 samples from 7 females; plasma: less than 1.0-35.4 ng/ml, 25 samples from 7 females). The latter group showed cyclic patterns of urinary progesterone, indicating a mean ovarian cycle length of 34.4 +/- 1.6 days (mean +/- s.e.m.) with a follicular phase of 6.0 +/- 0.6 days and a luteal phase of 27.5 +/- 1.3 days (19 cycles from 9 breeding females). In non-breeding females urinary and plasma progesterone values were undetectable (urine: less than 0.5 ng/mg Cr, 232 samples from 64 females; plasma: less than 1.0 ng/ml, 7 samples from 6 females). Breeding females had higher (P less than 0.001) plasma LH concentrations (3.0 +/- 0.2 mi.u./ml, 73 samples from 24 females) than did non-breeding females (1.6 +/- 0.1 mi.u./ml, 57 samples from 44 females). Urinary and plasma progesterone concentrations in non-breeding females from wild colonies situated near Mtito Andei, Kenya, were either below the assay sensitivity limit (urine: less than 0.5 ng/mg Cr, 11 females from 2 colonies; plasma: less than 1.0 ng/ml, 25 females from 4 colonies), or very low (plasma: 1.6 +/- 0.6 ng/ml, 15 females from 4 colonies). In captivity, non-breeding females removed from their colonies (i.e. the dominant breeding female) and either paired directly with a non-breeding male (N = 2), or removed and housed singly for 6 weeks before pairing with a non-breeding male (N = 5) may develop a perforate vagina for the first time in as little as 7 days. Urinary progesterone concentrations rose above 2.0 ng/mg Cr (indicative of a luteal phase) for the first time 8.0 +/- 1.9 days after being separated. These results suggest that ovulation is suppressed in subordinate non-breeding female naked mole-rats in captive and wild colonies, and show that plasma LH concentrations are significantly lower in these non-breeding females. This reproductive block in non-breeding females is readily reversible if the social factors suppressing reproduction are removed.     

Social influences on oestrous cycle length and plasma progesterone concentrations in the female lesser mouse lemur (Microcebus murinus)

Plasma progesterone concentrations were recorded during one breeding season in 19 lesser mouse lemur females living in different social conditions. The oestrous cycle length and the progesterone profile mainly depended on the social environment of the female. For totally isolated females, the oestrous cycle lasted 38 +/- 5.7 days and included a 25-30-days spontaneous luteal phase with a progesterone peak about 100 ng/ml between the 20th and 25th days after oestrus, and a prolonged preovulatory period of 10-15 days which could be considered equivalent to the follicular phase of a menstrual cycle. When females were able to communicate through olfactory, visual and auditory signals, the oestrous cycle was significantly lengthened (53.7 +/- 5.9 days). When females had tactile contacts, the oestrous cycle was further lengthened (62.7 +/- 0.8 days). This lengthening of the oestrous cycle was related to an extension of the luteal phase associated with a decrease in progesterone concentrations during this period. In females maintained with one male (paired) or with males and females (heterosexually grouped), large individual variations were shown in cycle lengths or in progesterone concentrations. In these females, cycle lengths and progesterone concentrations were inversely correlated to plasma cortisol concentrations.     

Endocrine and behavioral observations during transition of non-breeding into breeding season in female American bison (Bison bison)

This study provides endocrine data in relation to behavioral events during the transition of the non-breeding into the breeding season in American bison (Bison bison). Fecal progesterone metabolite patterns (20-oxo-P) were obtained in 13 adult female American bison and hormonal data were correlated with behavioral observations; i.e. copulation, male tending, female tail-up behavior and gestation length. Based on fecal progesterone metabolite patterns, the breeding season started between the middle of July and early August. Predictable short cycles reflected the transition from non-breeding to the breeding season; the luteal phase of these cycles was 4.10+/-0.86 days. Copulations and female tail-up behavior were reliably associated with the hormonally detected ovulation. Male tending behavior was more loosely associated with hormonally detected ovulation. The observed hormonal pattern in the study females indicated that 9 of 10 pregnant cows conceived during the second ovulatory period in the breeding season. One other cow conceived during her third ovulatory period, and one cow did not conceive until later in the breeding season by beginning of October. Gestation duration was on average 266.30+/-1.00 days. In summary, this study confirmed that the bison is a seasonally polyestrous species; the transition from the non-breeding into the breeding season was characterized by short cycles with low progesterone metabolite values.     

Controlling interrelationships of progesterone/LH and estradiol/LH in mares

The interrelationships of progesterone, estradiol, and LH were studied in mares (n=9), beginning at the first ovulation (Day 0) of an interovulatory interval. An increase in mean progesterone concentrations began on Day 0 and reached maximum on Day 6, with luteolysis beginning on Day 14. A common progesterone threshold concentration of about 2 ng/ml for a negative effect on LH occurred at the beginning and end of the luteal phase. Progesterone and LH concentrations decreased at a similar rate from Day 6 until the onset of luteolysis on Day 14, consistent with a decreasing positive effect of LH on progesterone. Concentrations of LH during the increase in the ovulatory surge consisted of two linear regression segments involving a rate of 0.4 ng/ml/day for Days 14-22 and 1.8 ng/ml/day for Day 22 to 1 day after the second ovulation. The end of the first segment and beginning of the second segment was 2 days before ovulation and was the day the ovulatory estradiol surge was at a peak.     

Annual changes of urinary progesterone and estradiol-17beta of the Dugong (Dugong dugon) in captivity

Levels of urinary progesterone and estradiol-17 beta were measured twice a week in a female dugong, Dugong dugon, in captivity for two years from April 1996 to April 1998. The dugong showed 14 ovarian cycles during the period of study. Concentrations of progesterone ranged from 0.01 ng/mg creatinine (Cr) to 1.94 ng/mg Cr and the length of estrous cycle was 53.6+/-8.6 (mean+/-SEM) days based on intervals of urinary progesterone peak-to-peak measurements. Concentrations of urinary estradiol-17 beta ranged from 0.9pg/mgCr to 23.7pg/mgCr, and tended to peak just prior to elevations of progesterone during the first year of study. This is the first report demonstrates that the ovulatory cycle of the dugong is about 50 days. The present findings suggest that measurement of urinary progesterone is a useful method to detect ovarian cycle of the dugong in captivity.     

Serum concentrations of oestradiol and progesterone during the normal oestrous cycle and early pregnancy in the lion (Panthera leo)

During a 6-month study period weekly serum samples demonstrated 9 oestradiol surges above 14 pg/ml (range 19-108 pg/ml) among 3 lionesses isolated from male lions. Intervals between peaks ranged from 3 to 8 weeks. Progesterone surges of more than 17 ng/ml (range 17-282 ng/ml) and lasting for 2-6 weeks were recorded after 7 of the oestradiol peaks. Sexual behaviour correlated well with the oestradiol peaks. Except for cornification following oestradiol peaks, there was no obvious vaginal cytology pattern at other times of the cycle. Pregnancy occurred after a 12-h contact with a male during behavioural oestrus. During gestation (108 days) oestradiol values remained low, while progesterone was elevated to 49 ng/ml within 12 h after mating, reaching a peak of 143 ng/ml at the 4th week, and remaining elevated during the next 2 months.     

Changes in serum FSH concentrations in the pig during development

Serum FSH concentrations were measured in fetal and prepubertal pigs between 40 days postcoitum and 25 weeks after birth. In addition, serum FSH was estimated in prepubertal, unilaterally cryptorchid, freemartin and castrated pigs. The average serum FSH concentrations in male and female fetuses was low (less than 2 ng/ml) until 80 days p.c. During the remaining fetal period, concentrations in females were elevated (7.9 +/- 0.4 ng/ml) and remained fairly constant after birth (16.3 +/- 0.8 ng/ml). In the male, serum FSH concentrations gradually rose to 22.5 +/- 5.5 ng/ml during the first 3 weeks after birth and declined thereafter. The changes in FSH concentrations in male pigs are reflected in gonadal-development. In contrast, in fetal and prepubertal females, ovarian development seems not to be influenced by changes in serum FSH concentrations. Unilateral cryptorchidism did not affect serum FSH concentrations. After castration, however, concentrations rose significantly. In freemartin pigs concentrations were similar to those in female pigs.     

Effects of larval tapeworm (Taenia taeniaeformis) infection on reproductive functions in male and female host rats

This report examined the effects of larval tapeworm infection on the reproductive functions in both male and female host rats. Female rats were matched by age, then randomly assigned to control and treatment groups (infected with larval tapeworms). Estrous cycles were determined by vaginal smear with 95% of the control group exhibiting 4-day normal cyclicity and only 55% of the treated group exhibiting normal cycles. Female fertility was then evaluated for the normally cycling rats based on the percentage of successful matings on the evening of proestrus, number of implantation sites on Day 8 of pregnancy, and number of pups born at term. The normally cycling rats exhibited 96% successful mating, 12.95 +/- 1.80 implantation sites, and 11.20 +/- 1.80 pups born. Five months after larval tapeworm infection, the fertility parameters were decreased to 79%, 9.10 +/- 1.20, and 7.50 +/- 1.50, respectively. The control females were then used in a study of male fertility after larval tapeworm infection employing the same parameters used to test female fertility. At the onset of the study, control groups exhibited 95% successful mating, 12.50 +/- 1.50 implantation sites, and 11.60 +/- 1.60 pups born at full term. After the 5-month infection period, the parameters were substantially reduced to 29%, 6.20 +/- 0.80 implantation sites, and 5.10 +/- 0.80 pups, respectively. Average testosterone concentrations in serum and testis from control male rats were 8.80 +/- 0.95 ng/ml and 3.88 +/- 0.25 ng/mg protein, respectively. After the 5-month infection period, these levels were reduced to 2.47 +/- 0.31 ng/ml and 1.28 +/- 0.12 ng/mg protein, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Early pregnancy diagnosis of captive Amur tigers (Panthera tigris altaica)

From January 2015 to February 2017, urine samples was collected from twelve captive female Amur tigers during both their mating (or receptive) periods and the first four weeks after mating at the Hengdaohezi Feline Breeding Center (FBC) in China. A radioimmunoassay was applied to determine the progesterone levels in the urine samples. The relationship between progesterone levels and pregnancy in Amur tigers was assessed according to whether the tigers gave birth in the end. Results showed that average progesterone levels increased significantly (P < .05) after mating for all female tigers having parturition. And the minimum value of progesterone levels of them during the fourth week after mating was consistently higher than 0.21 ng/mL, the maximum value in mating period of all female tigers. However, there were no significant differences in progesterone levels between mating period and the first four weeks after mating of the female tigers having no parturition. Therefore, early pregnancy in captive Amur tigers can be diagnosed when urine progesterone concentrations attain a level higher than 0.21 ng/mL for seven days in a row after mating.     

Exposure to ovarian steroids elicits a female pattern of plasma cortisol levels in castrated male macaques.

Our recent observations (1) that there is a difference in circadian patterns of plasma cortisol levels between male and female macaques and (2) that after gonadectomy these differences in the patterns and in the levels of cortisol were reduced prompted us to investigate how 17 beta-estradiol (E2) and progesterone affect cortisol secretion in orchidectomized male rhesus macaques. Five male macaques, castrated as adults, were implanted subcutaneously with segments of silastic tubing filled with E2 and with progesterone in a manner such that the levels and the sequence of these hormones mimicked those that occur during the menstrual cycle of intact female macaques. Since previous studies had shown that the difference in cortisol patterns was due to higher levels in females during the day, these studies were conducted from 0800 to 2000 hours. Blood samples were collected in an adjacent room at 15-minute intervals. Separate trials were conducted 2 weeks after E2 was implanted and levels were 110 +/- 14 pg/ml and again 2 weeks later after progesterone was implanted and E2 levels were 59 +/- 15 pg/ml; progesterone levels averaged 4.0 +/- 0.65 ng/ml. Mean plasma concentrations of cortisol (microgram/100 ml) for the 12-hour period were three-fold higher in orchidectomized males treated with E2 (17.2) and with E2 + progesterone (18.0) than in intact males (4.9). Levels in males treated with ovarian steroids were double that (8.5 micrograms/100 ml) observed for intact females.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serum 17β-estradiol and progesterone associated with mating behavior during early pregnancy in female rhesus monkeys

The phenomenon of postconception mating behavior was examined in a social group of rhesus monkeys living in an outdoor compound. Periodic blood samples and daily vaginal swabs were obtained from nine females beginning several weeks prior to conception and continuing through 6 weeks of pregnancy to permit an assessment of ovarian hormonal events associated with mating during early pregnancy. Each of the females showed a discrete period of copulatory activity during the periovulatory period which ceased within several days after the 17β-estradiol (E₂) ovulatory peak. In agreement with earlier reports, only a percentage of subjects (44%) exhibited a period of postconception mating, with copulatory activity beginning 19.8 (± 1.9) days following the E₂ peak and continuing for 9.5 (± 1.3 days). Implantation bleeding was detected in all of the subjects with the onset 19.5 (± 0.68) days after the E₂ peak. The interval between the E₂ peak and the onset of implantation bleeding was similar for all females. However, the duration of implantation bleeding was significantly shorter in females who exhibited postconception mating. The females who displayed postconception copulatory activity had significantly lower mean serum progesterone concentrations (2.33 ± 0.24 ng/ml vs. 3.64 ± 0.37 ng/ml) during the period associated with implantation bleeding and copulatory behavior. Although both groups had elevated concentrations of serum E₂ during this period, levels in the females who displayed postconception mating were significantly lower (173.8 ± 19.2 pg/ml vs 223.9 ± 28.8 pg/ml). These data demonstrate that the occurrence of postconception mating behavior in this environment is associated with a distinct pattern of ovarian hormonal events, and analysis suggests that differences in steroid concentrations probably account for the observed differences in implantation bleeding and copulatory behavior during pregnancy.     

Plasma concentration of progesterone and 17beta-estradiol of black-rumped agouti (Dasyprocta prymnolopha) during the estrous cycle

Plasma concentration of progesterone and 17beta-estradiol of black-rumped agouti (Dasyprocta prymnolopha) during the estrous cycle. The agouti is a game animal that have been raised in captivity for conservation and sustainability purposes. However, the management of wild animals in an intensive breeding system requires an assertive knowledge of its reproductive parameters, one of the most important features for production improvement. Besides, little information is available regarding changes in reproductive hormone profiles in agouti. The objective of this study was to evaluate the hormonal profile of progesterone and 17beta-estradiol during the estrous cycle of the agouti (Dasyprocta prymnolopha). The hormones were analyzed by radioimmunoassay. Blood samples were collected without sedation twice a week. The concentrations of progesterone were as follows: proestrus 0.78 +/- 0.39 ng/ml, estrus 2.83 +/- 2.34 ng/ml, metestrus 1.49 +/- 1.24 ng/ml, diestrus 3.71 +/- 1.48 ng/ml. In the estrous phase, an increase in the progesterone level was observed during a period of 24h. The average 17 beta-estradiol levels were as follows: proestrus 2 030.98 +/- 961.00 pg/ml, estrus 1 910.56 +/- 650.54 pg/ml, metestrus 1 724.83 +/- 767.28 pg/ml, diestrus 1 939.94 +/- 725.29 pg/ml. The current results suggest that the progesterone plasma concentration during the estrous cycle in the agouti has a similar increasing, stabilizing and decreasing pattern, as in domestic mammals. Agoutis have two phases of follicular development, as two periods of 17beta-estradiol peaks were observed, the first one in the metestrus and the second during the proestrus. Spontaneous ovulation seems to occur after the progesterone peak, possibly indicating that this hormone is associated with the ovulatory process. A more detailed investigation is needed for better understanding of how progesterone influences ovulation. Studies on the involvement of progesterone in follicular rupture can be carried out, using steroid biosynthesis inhibitors and observing the effect of this hormone on ovarian activity of proteolytic enzymes in the follicular wall.     

Evaluation of an ovarian synchronization scheme for fixed-time artificial insemination in wapiti

The ovarian response to an empirically derived treatment protocol used commercially for fixed-time insemination in wapiti (Cervus elaphus) was evaluated by transrectal ultrasonography in hinds during transition into the ovulatory season. On September 29, hinds (n=7) were given an intravaginal progesterone-releasing device (CIDR-B, 1.9 g of progesterone) or left untreated (controls, n=9). Fourteen days later, hinds in the treated group were given 200 IU eCG and the CIDR was removed. Hinds in the control group ovulated randomly over a 15 day period. In the treated group, five hinds ovulated 3 days after eCG treatment, one ovulated 7 days after treatment, and one failed to ovulate by November 1. All extant dominant follicles ceased growth and/or began to regress within 2 days of CIDR placement. Two waves of follicular development were detected between CIDR insertion and removal; the first emerged 5.1+/-0.5 days after CIDR insertion and the second at 11.0+/-0.7 days. Serum progesterone concentration was 0.6+/-0.5 ng/mL (range 1.0-0.3 ng/mL) before CIDR placement, remained above 6 ng/mL during CIDR placement, and fell to 0.8+/-0.9 ng/mL after CIDR removal. In the control group, maximal luteal-phase progesterone concentration was lower (1.1+/-0.1 ng/mL; P<0.05) and emergence of the first follicular wave was more variable (P=0.05) than in the treated group. The protocol to synchronize ovulation was effective in 5/7 (71%) hinds, and 4/7 (57%) became pregnant and calved. The pregnancy rate (6/9) and calving rate (5/9) was similar in the control group. In conclusion, synchronization with CIDR-B was effective; however, the protocol may be improved by shortening the interval of CIDR placement to < or = 7 days and by reducing the circulating concentrations of progesterone to physiologic concentrations (< 4 ng/mL).