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1.
Reasons for performing the study: The maternal recognition of pregnancy (MRP) signal in the mare has not been determined, although oestrogens have been proposed as a potential candidate. Objectives: To determine effects of intrauterine administration of oestrogen and various oils on cyclic luteolysis in the mare. Hypothesis: Intrauterine oestradiol or fatty acids may suppress luteolysis in the cycling mare when administered during late dioestrus. Methods: A single 1 ml dose of slow‐release oestradiol (10 mg/ml) in fractionated coconut oil was infused into the uterine lumen of cycling mares on Days 6, 8, 10, 12 or 14 post ovulation (n = 12 in each group). Four further groups, each of 12 mares, received an intrauterine infusion of either 1 ml of fractionated coconut oil, peanut oil, mineral oil or a slow‐release preparation of oestradiol (10 mg/ml) in mineral oil on Day 10 post ovulation. Serial blood samples were assayed for progesterone concentrations to monitor luteal function. Results: Intrauterine administration of oestradiol in fractionated coconut oil showed peak efficacy at Day 10 when luteolysis was delayed in 11/12 (92%) mares. The ability of the treatment to delay luteolysis was not significantly different when administered on Days 8 (9/12; 75%), 12 (10/12; 83%) or 14 (6/12; 50%) of dioestrus, but declined significantly when given on Day 6 (3/12; 25%). Oestradiol was not needed to initiate luteostasis since fractionated coconut oil alone or peanut oil administered at Day 10 induced the same high rate of luteal persistence (11/12; 92% for both oils). In contrast, mineral oil did not prolong luteal lifespan, either when administered alone (2/12; 17%) or combined with oestradiol (3/12; 25%). Conclusion: These results do not unequivocally rule out a possible involvement of embryonic oestrogens in MRP in the mare but suggest it is unlikely. The results demonstrate that plant oils can postpone luteolysis, suggesting they may modulate synthesis or release of prostaglandins from the mare's endometrium. Potential relevance: Administration of fractionated coconut or peanut oil on Day 10 post ovulation provides an effective and practical method of prolonging luteal function (‘pseudopregnancy’) thereby suppressing unwanted oestrous behaviour. Further studies to elucidate the mechanism by which this is achieved may increase understanding of both luteostasis and MRP signal in the mare.  相似文献   

2.
The concentrations of follicle stimulating hormone, luteinising hormone and progesterone were measured in serial blood samples taken throughout one or more oestrous cycles from 12 Thoroughbred mares, some of which exhibited single and others twin ovulations. The resulting profiles clearly demonstrated that no simple relationship exists between circulating gonadotrophin levels and subsequent ovulation rate in the mare. However, plasma progesterone concentrations during dioestrus are, as expected, higher following twin than single ovulations. The findings suggest that the underlying cause of twin ovulation in some mares may exist at the ovarian end of the pituitary-ovarian axis which controls follicular development and ovulation.  相似文献   

3.
A factor responsible for progression to pregnancy establishment in the mare has not been definitively characterized. To identify factors possibly involved in the establishment of equine pregnancy, the endometrium was collected from day 13 (day 0=day of ovulation) cyclic and day 13, 19 and 25 pregnant animals. From initial subtractive hybridization studies, a calcium regulating factor, Stanniocalcin-1 (STC1) mRNA, was found as a candidate molecule expressed uniquely in the pregnant endometrium. Endometrial expression of STC1 mRNA was noted on day 19 and was markedly increased in the day 25 gravid endometrium. STC1 protein was found in the extracts of day 25 gravid endometrium and immunochemically localized in the uterine glands. In addition, STC1 protein was detected in uterine flushing media collected from day 25 pregnant mares. High concentrations of estradiol-17 β (E(2)) were detected in day 25 conceptuses. E(2) levels were much higher in the gravid endometrium than in other regions, whereas progesterone levels did not differ among the samples from different endometrial regions. Expression of STC1 mRNA, however, was not significantly upregulated in cultured endometrial explants treated with various concentrations of E(2) (0.01-100 ng/ml) with or without 10 ng/ml progesterone. These results indicate that an increase in STC1 expression appears to coincide with capsule disappearance in the conceptus, and suggest that STC1 from the uterine glands likely plays a role in conceptus development during the pregnancy establishment period in the mare.  相似文献   

4.
The effects of a low dose of equine purified FSH (eFSH) on incidence of multiple ovulations and embryo recovery rate in mares were studied. During the physiological breeding season in Brazil (19°45′45′S), 14 Mangalarga Marchador donor mares were used in a crossover study and another 25 mares of the same breed, between 3 years and 12 years of age were used as recipients for the embryo transfers. Donors were monitored during two consecutive oestrus cycles, an untreated control cycle followed by a treated cycle, when eFSH was administered. In both cycles, after an embryo collection attempt on day 8 post‐ovulation all mares received 7.5 mg dinoprost and had their two largest follicles tracked daily by ultrasonography until the period of ovulation. Mares were inseminated every 48 h with extended fresh semen from a single stallion after the identification of a 35‐mm follicle until the period of ovulation. Ovulations were induced by intravenous administration of 2.500 IU of human chorionic gonadotropin, upon detection of a 35‐ to 40‐mm follicle. In the treated cycle, 5 mg eFSH was given intramuscularly once a day, from day 8 post previous ovulation until at least one follicle reached 35 mm in diameter. Embryo flushes were performed on day 8 of dioestrus (day 0 = ovulation). Treatment with eFSH resulted in higher (p < 0.05) ovulation rate and incidence of multiple ovulations compared to the control (1.6 vs 1.0 and 50% vs 0%, respectively – one mare had triple ovulation). However, embryo recovery rates in the control and treated cycles were similar (0.8 and 1.0, respectively; p > 0.05). Pregnancy rates in the recipient mares following embryo transfer were similar for the control and eFSH cycles (11/11 and 10/14, respectively). Additional studies are necessary in order to develop a low‐dose protocol for the use of eFSH that brings a more consistent contribution to the efficiency of commercial equine embryo transfer programs.  相似文献   

5.
The present study aimed to investigate the pathogenesis of cystic ovarian disease (COD) in high-yielding dairy cows postpartum (pp). Hormonal and metabolic profiles during the first 3 weeks pp as well as during the final week prior to ovulation/cyst formation, were compared between dairy cows that developed either an ovulatory follicle (OV) or a cyst (CYST) < day 60 pp. Thirty-four lactations of 28 high-yielding (9500 kg/305 days) Holstein-Friesian dairy cows were studied. Ovaries of cows were scanned twice a week from day 10 pp on, until ovulation/cyst formation. Milk yield data, body condition scores and blood samples, for determination of oestradiol-17beta, insulin, beta-OH-butyrate and non-esterified fatty acids, were collected simultaneously. Milk samples for progesterone analysis were collected daily. Four lactations were excluded from further analysis because of irregular pp ovarian cyclicity, excluding COD. Eight lactations (26.7%) developed a cyst, while 22 lactations ovulated < days 60 pp. Ovulation and cyst formation occurred at similar times pp. Metabolic and hormonal profiles did not differ between CYST and OV lactations during the first 3 weeks pp. In the final week prior to cyst formation/ovulation, insulin concentrations were lower in CYST than in OV lactations while no differences were observed for any of the other parameters tested. In two lactations, cyst formation was preceded by suprabasal progesterone and increased oestradiol-17beta concentrations. These results suggest that cyst formation in high-yielding dairy cows pp is associated with lower insulin levels but not with other distinct hormonal and metabolic alterations. However from this study, we cannot exclude the involvement of subtle hormonal and metabolic changes in the pathogenesis of ovarian cysts. Suprabasal progesterone, and altered oestradiol-17beta concentrations, seem to play a minor role in cyst formation.  相似文献   

6.
In its first year of commercial availability in the United States, reports from the field indicated that Ovuplant™ (a deslorelin-containing slow-release implant for hastening ovulation in mares) was associated with a delayed return to estrus in mares not becoming pregnant. Supposedly this effect was particularly prevalent in mares subsequently administered PGF2α to cause luteal regression after embryo collection. The present experiment was conducted 1) to determine if the field observations were repeatable under controlled experimental conditions, and 2) to gather endocrine data that might yield information on the underlying cause(s) of this observation. Twenty-five light horse mares were used. Ovaries of each mare were examined by transrectal ultrasonography daily during estrus until ovulation. Once a follicle >30 mm was detected, the mare received either Ovuplant (treated group; N = 13) at the recommended dosage or a sham injection (controls; N = 12); treatments were administered in a manner to ensure that they were unknown to personnel involved with data collection. On day 7 after ovulation, each mare received a luteolytic injection of PGF2ð. Mares were examined every other day until return to estrus or development of a 30 mm follicle, at which time daily examination was performed until ovulation. Jugular blood samples were collected daily. Two mares receiving Ovuplant did not return to estrus within 30 days and their data were not included in the statistical analyses; in contrast, no control mare exhibited such an extended interovulatory interval. For all other mares receiving Ovuplant, the interval between the first and second ovulations was longer (P = .0001) than that of control mares by an average of 6.2 days. In addition, plasma LH concentrations were lower (P <.05) in the treated mares on days 0 through 4, 9, 11, 18, and 19 after the first ovulation. Plasma FSH concentrations were also lower (P = .017) in treated mares from days 4 to 11 and on days 6 and 5 prior to the second ovulation (P = .005). Differences in progesterone and estradiol were observed but were less consistent than for LH and FSH. Mares receiving Ovuplant had fewer small (P =.026), medium (P = .003) and large (P = .045) follicles prior to the second ovulation. In conclusion, Ovuplant treatment at the recommended dosage decreased follicular activity after ovulation and increased the interovulatory interval in mares short-cycled with PGF2ð. These effects appear to be mediated by a hyposecretion of LH and(or) FSH.  相似文献   

7.
A replicated trial was conducted with suckled Angus and Polled Hereford cows (110 d postcalving) to determine metabolic and endocrine responses to an energy-restricted diet after cows had re-established postpartum estrous cyclicity. Cows were individually fed 26.5 Mcal ME (H) or 15.2 Mcal ME (L) for a 30-d preliminary period and fitted with an indwelling jugular cannula at synchronized estrus. Average daily weight change during the estrous cycle was .60 +/- .25 and -1.37 +/- .30 kg/d for H and L, respectively (P less than .05). Blood concentrations of cortisol, progesterone and LH during the estrous cycle were not affected by diet, nor did diet affect frequency or amplitude of LH pulses (P greater than .05). No dietary differences were observed for daily concentrations of total protein, glucose, nonesterified fatty acids or acetate. Mean blood concentrations of propionate and butyrate were not different between diets; however, L cows had lower concentrations of propionate and butyrate on d 11 of the cycle (P less than .05). Cows fed L had higher concentrations of blood urea nitrogen (P less than .05), but they had lower concentrations of cholesterol (P less than .05) on d 4, 11, 18 and subsequent estrus (E). Insulin was not different on d 4 and 11; however, cows fed L had lower insulin concentrations on d 18 and d E (P less than .05). Dietary energy restriction in these cyclic cows caused no change in endocrine responses. Of metabolic responses measured, only blood urea nitrogen, cholesterol and insulin showed consistent changes.  相似文献   

8.
Equine follicle stimulating hormone (FSH) and luteinizing hormone (LH) were measured in the serum obtained from pregnant mares, bled daily, from up to 17 days before parturition until the first ovulation after parturition. LH was at baseline levels until 2 days before ovulation when it started, and continued, to rise until after ovulation. FSH surges occurred at approximately 24 and 14 days before this post-partum ovulation (12 and 2 days before parturition), thus showing a similar pattern to the cyclic mare, consistent with the hypothesis that 2 surges at these times prepare and prime follicles for subsequent ovulation. The high plasma oestradiol levels that occurred during and immediately before these FSH surges did not show a negative feedback, or the inverse relationship between FSH and oestradiol which occurs in the cyclic mare, and in other species.  相似文献   

9.
Aglepristone was administered in bitches during the follicular phase to evaluate its effects on progesterone, estradiol-17β and LH serum concentrations. Ten German Shepherds were divided into two groups (treated n = 5; control n = 5). Treated bitches received 10 mg/kg BW of aglepristone subcutaneously during the early follicular phase, 24 hr after and then 7 days later. The control group was injected, at the same time periods, with saline solution (0.3 ml/kg BW). For the steroid evaluations, blood was collected daily from the onset of proestrus until the first day of cytological dioestrus. For LH base-line serum determination, blood was also collected every 20 min for 2 hr at the onset of proestrus. For LH surge identification, blood was collected daily (every 6 hr) starting from the day of the first administration of aglepristone or saline solution until the first day of dioestrus. All animals ovulated but the treated group presented longer ovulation-dioestrus intervals than the control group (5.2 ± 2.2 days p < .05). Serum concentrations of the evaluated hormones were similar between experimental animals except for serum LH. Indeed, no LH peaks were detected in the treated group while LH surges were clearly observed in the control group (9 ± 1 days after the beginning of proestrus. In particular, the area under the curve for LH was significantly lower in treated than control animals (12 ± 4 ng/ml x Day; p = .01). In conclusion, administrations of aglepristone during the follicular phase of the bitch does not affect the steroid hormone patterns but does prevent the occurrence of a LH surge. This work raises significant questions and opens perspectives concerning the mechanisms of ovulation in bitches.  相似文献   

10.
The effect of cracked corn grain supplementation (3.5 kg/day) during 3 weeks before the expected calving date on milk production and composition, body condition score (BCS), metabolic and hormonal profiles and length of postpartum anoestrus was evaluated in multiparous Holstein dairy cows under grazing conditions (Energy supplemented group, n = 10; Control group, n = 10). Body condition score was weekly recorded during the peripartum period, from days −21 to +35 (parturition = day 0). Non-esterified fatty acids, β-hydroxybutyrate, cholesterol, urea, insulin, insulin-like growth factor I (IGF-I), leptin, thyroxine (T4) and 3,3'5-triiodothyroinine (T3) were weekly determined in plasma from days −21 to +35. The reinitiation of ovarian cyclicity was twice weekly determined by ovarian ultrasonography and confirmed by plasma progesterone concentrations. Cows fed energy concentrate prepartum had higher BCS during the prepartum and postpartum and produced more milk. Non-esterified fatty acids plasma concentrations were significantly higher in the energy group, while cholesterol was higher in the control group. Treated cows had higher levels of plasma insulin, IGF-I and leptin pre-calving. IGF-I, leptin and T4 were diminished during the early postpartum period in both groups. Insulin levels were also diminished in the control group, but levels remained high in the energy-supplemented group. Treated cows ovulated sooner after parturition than controls. We conclude that Energetic supplementation prepartum in cows under grazing conditions increased milk production and reduced the reinitiation of ovarian activity, consistent with a better EB (BCS), higher prepartum levels of IGF-I, leptin and insulin, and higher insulin levels during early postpartum.  相似文献   

11.
Two juvenile (9 months) and two adult (3 years) beagle bitches were injected with five doses (250 i.u. per dose) of pregnant mare serum gonadotrophin (PMSG) on alternate days. Plasma oestrogen concentrations rose in all bitches. In one adult bitch plasma progesterone concentrations remained basal and no signs of oestrus were shown; in the other there was a slight elevation of circulating progesterone values and she showed oestrus but did not conceive. Both the young bitches came into heat and had multiple ovulations, producing very high plasma progesterone concentrations. One of them conceived, and at laparotomy on the thirty-sixth day after the first mating seventeen conceptuses were seen; 14 days later ovarohysterectomy was performed and only five foetuses remained in the uterus.  相似文献   

12.
To get more insight in how insulin secretion patterns and corresponding insulin-like growth factor-1 (IGF-1) levels are related to luteinizing hormone (LH) secretion, follicle development and ovulation, 32 multiparous sows were fed either a dextrose plus lactose-containing diet at 4 h intervals (DL; each 150 g/day) or an isocaloric control diet at 12 h intervals (CTRL; containing soybean oil) during the weaning-to-ovulation interval (WOI). Insulin parameters (basal, peak levels and mean insulin) and IGF-1 levels during the WOI were similar for both treatments, but the insulin secretion pattern differed (related with feeding frequency and meal sizes). Oestrus and ovulation characteristics were not influenced by treatment. The LH surge was higher in CTRL compared with DL sows (3.73 vs 3.00 ng/ml; p = 0.03). Average diameter (6.5 vs 6.1 mm; p = 0.08) and uniformity (CV: 11 vs 15%, p = 0.02) of follicles ≥3 mm at day 4 after weaning was higher in CTRL compared with DL sows. Basal insulin levels were positively related with follicle diameter at ovulation (β = 0.05 mm/(μU/ml); p = 0.04) and negatively related with LH surge level (β = -0.07 (ng/ml)/(μU/ml); p = 0.01). Insulin area under the curve (AUC) (β = 0.037 (ng/ml)/1000 μU; p = 0.02) and IGF-1 levels (β = 0.002 (ng/ml)/(ng/ml); p < 0.01) were positively related to basal LH level around the LH surge. From these data, we conclude that insulin and IGF-1 levels during the WOI are related to LH secretion and follicle development. Not only the absolute level of insulin seems important, but also the pattern within a day in which insulin is secreted seems to affect LH secretion and development of pre-ovulatory follicles.  相似文献   

13.
The expression of 12 different aquaporin subtypes in equine endometrium was examined at the mRNA and protein level. Endometrial samples were obtained during anoestrus, oestrus, 8, and 14 days after ovulation in non‐pregnant mares, and 14 days after ovulation in pregnant mares. Quantitative PCR revealed a time‐dependent pattern for all aquaporin subtypes examined except for AQP10 and 12. AQP3, 5 and 7 showed highest mRNA abundance 8 days after ovulation, while AQP0 and 2 were most abundant at Day 14 of the cycle in non‐pregnant mares. At 14 days of pregnancy, AQP1, 4, 8, 9 and 11 displayed highest expression levels. Western blot analysis confirmed protein expression of AQP0, 2 and 5. Immunohistochemistry localized protein expression to luminal and glandular epithelial and stromal cells. AQP0 staining intensity was highest in samples obtained on Day 14 of the oestrous cycle. AQP2 immunoreactivity seemed to be stronger in samples collected 14 days after ovulation from non‐pregnant animals, in particular luminal epithelial staining. Samples collected 8 days after ovulation from cyclic animals were characterized by intense AQP5 staining of glandular epithelium, predominantly in the deeper glands. Progesterone treatment of anoestrous mares did not enhance expression of AQPs, indicating that factors other than progesterone are required for the up‐regulation of certain AQP subtypes during dioestrus. In conclusion, it seems that an equine‐specific collaboration of aquaporin subtypes contributes to changes in endometrial fluid content occurring throughout the oestrous cycle and contributes to endometrial receptivity during early pregnancy in the mare.  相似文献   

14.
The aims of this study were to assess the precision of the estimates of the time of ovulation derived by various methods, and to define the most appropriate methods for the determination of the optimal time for insemination of bitches with fresh semen (artificial insemination or natural mating), or with frozen-thawed semen. In 11 Labrador bitches, ovulation was estimated (plasma LH surge + 48 h) to occur 9 to 20 d after the start of the cycle, 0 to +4 d after the onset of positive postural reflexes (2 bitches showed no positive postural reflexes), -4 to +7 d after reaching a vaginal cytological eosinophilic index (EI) of 100%, over a range of 2.5 to 5.5 d based on plasma progesterone concentrations of 4 to 10 ng/ml, over a range of 2 to 3 or 4 d based on 2 indirect methods of estimating the time of the plasma LH surge from plasma progesterone concentrations. Assuming fertilisation occurs 2 to 3 d after ovulation, these findings indicate that for fresh semen (with an estimated lifespan of greater than 4 days) an appropriate procedure would be to inseminate/mate on the day after the onset of positive postural reflexes; then 3 days later. For bitches not showing positive postural reflexes, insemination should occur when the vaginal EI = 90% and then each 3 d until day 1 of dioestrus (D1). For frozen-thawed semen (with a lifespan of less than 24 h) insemination should occur 4 to 5 d after the plasma LH surge.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

15.
Premature luteal demise or luteal insufficiency is not well characterised as a cause of pregnancy loss in domestic species, including horses. In this report, a mare inseminated with cooled‐transported semen at our facility returned for a routine pregnancy diagnosis at 15 days post ovulation. Ultrasonography per rectum revealed endometrial oedema and the absence of visual indication of a corpus luteum on either ovary. Nonetheless, an embryonic vesicle small for the gestational age was identified. Daily oral altrenogest treatment was implemented immediately. Serum progesterone concentration was 0.67 ng/ml, which is below the threshold considered adequate for pregnancy maintenance in the mare. Examinations were repeated at 17, 25, 30, 39, 49, 72 and 120 days post ovulation. At 25 days post ovulation the embryonic vesicle presented normal development for the gestational age. In addition, sequential blood samples were collected to measure progesterone, equine chorionic gonadotrophin and oestrone sulphate concentrations. Although progesterone concentration did not exceed 2 ng/ml until 72 days post ovulation, all other results were unremarkable and a healthy filly was born uneventfully at 344 days post ovulation.  相似文献   

16.
Two experiments were conducted to determine if administration of progesterone within a low, subluteal range (0.1-1.0 ng/mL) blocks the luteinizing hormone (LH) surge (experiments 1 and 2) and ovulation (experiment 2) in lactating dairy cows. In experiment 1, progesterone was administered to cycling, lactating dairy cows during the luteal phase of the estrous cycle using a controlled internal drug release (CIDR) device. CIDRs were pre-incubated in other cows for either 0 (CIDR-0), 14 (CIDR-14) or 28 days (CIDR-28). One group of cows received no CIDRs and served as controls. One day after CIDR insertion, luteolysis was induced by two injections of prostaglandin (PG) F(2alpha) (25 mg) at 12 h intervals. Two days after the first injection, estradiol cypionate (ECP; 3 mg) was injected to induce a LH surge. Concentrations of progesterone after luteolysis were 0.11, 0.45, 0.78 and 1.20 ng/mL for cows treated with no CIDR, CIDR-28, CIDR-14, and CIDR-0, respectively. LH surges were detected in 4/4 controls, 4/5 CIDR-28, 2/5 CIDR-14 and 0/5 CIDR-0 cows following ECP. In experiment 2, progesterone was administered to cycling, lactating, Holstein cows during the luteal phase of the estrous cycle as in experiment 1. Luteolysis was induced as in experiment 1. The occurrence of an endogenous LH surge and ovulation were monitored for 7 days. Concentrations of progesterone after luteolysis were 0.13, 0.30, 0.70 and 1.20 ng/mL for cows treated with no CIDR, CIDR-28, CIDR-14 and CIDR-0, respectively. LH surges and ovulation were detected in 5/5 controls, 3/7 CIDR-28, 0/5 CIDR-14 and 0/5 CIDR-0 cows. It was concluded that low concentrations of progesterone can reduce the ability of either endogenous or exogenous estradiol to induce a preovulatory surge of LH and ovulation.  相似文献   

17.
To identify factors involved in the establishment of pregnancy in the mare, endometrium was collected from day 13 (day 0 = day of ovulation) cyclic and day 13, 19, and 25 pregnant animals. From initial cDNA subtraction studies, interleukin-1 receptor antagonist (IL-1RN) mRNA was found as a candidate molecule expressed uniquely in the pregnant endometrium. Expression of IL-1RN mRNA was markedly increased in day 19 and 25 gravid endometrium. In situ hybridization analysis revealed that IL-1RN mRNA was localized to the glandular epithelium. Interleukin-1 receptor antagonist (IL-1RN) protein was found in the extracts of day 25 gravid endometrium and was immunochemically localized to the glandular epithelium/luminal cavity of the pregnant uterus. High concentrations of estradiol-17β (E2) were detected in day 25 conceptuses. Concentrations of E2 were higher in the gravid endometrial portion than in other endometrial regions. On the other hand, progesterone concentrations did not differ among endometrial samples analyzed. Furthermore, the expression of IL-1RN mRNA was up-regulated in endometrium culture samples treated with 10 ng/mL E2 and 10 ng/mL progesterone. In the analysis of related gene expression, increased amounts of IL-1α and IL-6 mRNA were also found in the day 25 gravid endometrium; however, these expressions in endometrial culture samples were not up-regulated by the steroid treatment. These results indicate that expression of IL-1RN in the endometrium is likely regulated by E2 and progesterone and suggest that IL-1RN regulates the degree of IL-1 signal transduction and thereby plays an important role in the establishment of equine pregnancy.  相似文献   

18.
To study the possible role of ovarian androgens in regulation of follicle stimulating hormone (FSH) secretion in the cycling mare, five mature, intact mares were treated with testosterone (20 micrograms/kg of body weight) daily during estrus; five control mares received safflower oil on the same schedule. Mares were teased for estrus and samples of jugular blood were drawn daily through one full estrous cycle. Concentrations of FSH in plasma were measured by a newly developed radioimmunoassay based on anti-ovine FSH serum and radioiodinated equine FSH. Testosterone treatment during estrus had no effect on duration of estrus, diestrus or the total cycle. Concentrations of FSH in plasma during estrus were unaffected by testosterone treatment. However, FSH concentrations in testosterone-treated mares were elevated (P less than .05) compared with controls during mid-diestrus (d 6 through 11). The magnitude and timing of the LH peaks were unaffected by treatment, as was the day on which the first elevated progesterone concentration occurred. These data are consistent with a model of FSH secretion in which ovarian androgens cause an accumulation of FSH in the pituitary during estrus in preparation for the surges that occur in FSH secretion during diestrus.  相似文献   

19.
There is a need for a safe, effective and practical method of oestrus suppression in the mare. The aim of this study was to monitor ovarian activity in mares exposed to either 9.4 or 28.2 mg deslorelin acetate, a GnRH agonist, in the form of a sustained-release implant. Following oestrus synchronisation, mares were randomly assigned to one of three groups (n = 4 per group) and administered either one (Des1 group; 9.4 mg) or three (Des3 group; 28.2 mg) implants of deslorelin acetate (Suprelorin-12, Virbac Australia) or one blank implant (Control group; Virbac Australia). Mares underwent weekly blood sampling for 12 weeks following implant placement (Day 0–Day 84), with transrectal palpation and ultrasonography of the reproductive tract at all sampling timepoints except Days 56, 70 and 77. All mares showed baseline serum progesterone concentrations (SPC; ≤1.3 nmol/L or 0.4 ng/ml) on Day 0. Cycling Control mares showed typical oestrous cyclicity characterised by peaks and troughs in SPC over time. Four of eight treated mares demonstrated a sustained elevation in SPC after the initial ovulation after implant placement; SPC declined to baseline levels (Des1 group; 2 mares) or remained elevated (Des3 group; 2 mares) at the final sampling timepoint on Day 84. Oestrous cyclicity was erratic in three of the remaining four treated mares. In total, 87.5% (7 of 8) of treated mares showed atypical oestrous cyclicity after implant placement. These results suggest that deslorelin acetate disrupts oestrous cyclicity in the mare, which warrants further research.  相似文献   

20.
Two experiments studied the effects of pretreatment with estradiol benzoate before treatment with a dopamine antagonist on prolactin secretion and reproductive traits in mares during (1) the seasonal anovulatory period and (2) the normal breeding season. Experiment 1 was performed in winter with 17 mares selected for low follicular activity. Nine mares received estradiol benzoate injections every other day for a total of 10 injections; 8 mares received similar injections of vehicle. Ten days after onset of injections, all mares were placed on daily injections of sulpiride (250 mg) for 35 days or until ovulation. Plasma prolactin concentrations were higher (P < .001) in mares receiving estradiol than in controls for all assessments from days 12 through 36. Plasma luteinizing hormone (LH) concentrations were also increased (P < .05) by estradiol treatment from days 14 to 23. Mean day of first ovulation was 73.6 for control mares and 29.0 for estradiol-treated mares (P = .016). Estradiol treatment greatly enhanced prolactin secretion in response to sulpiride and increased LH secretion in seasonally anovulatory mares, which together hastened the date of first ovulation by an average of 45 days. Experiment 2 was designed to assess the efficacy of a long-acting, single-injection microparticle preparation of another dopamine antagonist, domperidone, for increasing prolactin secretion in cyclic mares in the summer. The experimental design and procedures used in experiment 1 were repeated, except that a single 3-g domperidone-microparticle injection was administered on day 11 rather than 45 days of sulpiride injections. Day 0 was the first day of estrus for each mare. Prolactin concentrations were higher (P < .05) in mares receiving estradiol than in control mares from days 12 through 25 and after a thyrotropin-releasing hormone injection on d 21. Estrous cycle traits (time to ovulation and time of luteal regression) were not affected (P > .1) by treatment. Estradiol enhanced the prolactin response to a single injection of 3 g domperidone in cyclic mares in the summer in a manner similar to the estradiol enhancement of prolactin secretion in response to daily sulpiride injections in anovulatory mares in winter. Thus, the single injection of domperidone could possibly replace the daily sulpiride injections used in experiment 1 to induce ovulation in seasonally anovulatory mares; this needs to be tested in future experiments.  相似文献   

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