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1.
Equine clinicians rely on ovulation induction agents to provide a timed ovulation in mares for optimal breeding management. Numerous studies have been performed on the efficacy of human chorionic gonadotropin (hCG) to induce ovulation in the mare, but limited clinical data are available for the new deslorelin acetate product SucroMate. This study was designed to evaluate the efficacy of SucroMate (deslorelin) in comparison with hCG to induce ovulation. American Quarter horse mares (n = 256) presented to Colorado State University for breeding management were used in this study. Mares received either deslorelin or hCG when a follicle ≥35 mm was detected by transrectal ultrasound in the presence of uterine edema. Ultrasonographic examinations were subsequently performed once daily until ovulation was detected. Deslorelin was administered to 138 mares during168 estrous cycles, and hCG was given to 118 mares during 136 estrous cycles. Mares administered deslorelin had a similar (P < .05) higher ovulation rate (89.9%) within 48 hours following drug administration than mares administered hCG (82.8%). There are no effects of season or age on ovulation rates in either treatment group. Twenty-one mares administered deslorelin and 11 mares administered hCG were monitored by transrectal ultrasound every 6 hours to detect ovulation as part of a frozen semen management program. Average intervals from deslorelin or hCG administration to ovulation were 41.4 ± 9.4 and 44.4 ± 16.5 hours, respectively. Results of this study indicate that SucroMate is effective at inducing a timed ovulation in the mare.  相似文献   

2.
Superovulation would potentially increase the efficiency and decrease the cost of embryo transfer by increasing embryo collection rates. Other potential clinical applications include improving pregnancy rates from frozen semen, treatment of subfertility in stallions and mares, and induction of ovulation in transitional mares. The objective of this study was to evaluate the efficacy of purified equine follicle stimulating hormone (eFSH; Bioniche Animal Health USA, Inc., Athens, GA) in inducing superovulation in cycling mares. In the first experiment, 49 normal, cycling mares were used in a study at Colorado State University. Mares were assigned to 1 of 3 groups: group 1, controls (n = 29) and groups 2 and 3, eFSH-treated (n = 10/group). Treated mares were administered 25 mg of eFSH twice daily beginning 5 or 6 days after ovulation (group 2). Mares received 250 (of cloprostenol on the second day of eFSH treatment. Administration of eFSH continued until the majority of follicles reached a diameter of 35 mm, at which time a deslorelin implant was administered. Group 3 mares (n = 10) received 12 mg of eFSH twice daily starting on day 5 or 6. The treatment regimen was identical to that of group 2. Mares in all 3 groups were bred with semen from 1 of 4 stallions. Pregnancy status was determined at 14 to 16 days after ovulation.In experiment 2, 16 light-horse mares were used during the physiologic breeding season in Brazil. On the first cycle, mares served as controls, and on the second cycle, mares were administered 12 mg of eFSH twice daily until a majority of follicles were 35 mm in diameter, at which time human chorionic gonadotropin (hCG) was administered. Mares were inseminated on both cycles, and embryo collection attempts were performed 7 or 8 days after ovulation.Mares treated with 25 mg of eFSH developed a greater number of follicles (35 mm) and ovulated a greater number of follicles than control mares. However, the number of pregnancies obtained per mare was not different between control mares and those receiving 25 mg of eFSH twice daily. Mares treated with 12 mg of eFSH and administered either hCG or deslorelin also developed more follicles than untreated controls. Mares receiving eFSH followed by hCG ovulated a greater number of follicles than control mares, whereas the number of ovulations from mares receiving eFSH followed by deslorelin was similar to that of control mares. Pregnancy rate for mares induced to ovulate with hCG was higher than that of control mares, whereas the pregnancy rate for eFSH-treated mares induced to ovulate with deslorelin did not differ from that of the controls. Overall, 80% of mares administered eFSH had multiple ovulations compared with 10.3% of the control mares.In experiment 2, the number of large follicles was greater in the eFSH-treated cycle than the previous untreated cycle. In addition, the number of ovulations during the cycle in which mares were treated with eFSH was greater (3.6) than for the control cycle (1.0). The average number of embryos recovered per mare for the eFSH cycle (1.9 ± 0.3) was greater than the embryo recovery rate for the control cycle (0.5 ± 0.3).In summary, the highest ovulation and the highest pregnancy and embryo recovery rates were obtained after administration of 12 mg of eFSH twice daily followed by 2500 IU of hCG. Superovulation with eFSH increased pregnancy rate and embryo recovery rate and, thus, the efficiency of the embryo transfer program.

Introduction

Induction of multiple ovulations or superovulation has been an elusive goal in the mare. Superovulation would potentially increase the efficiency and decrease the cost of embryo transfer by increasing embryo collection rates.[1 and 2] Superovulation also has been suggested as a critical requirement for other types of assisted reproductive technology in the horse, including oocyte transfer and gamete intrafallopian transfer. [2 and 3] Unfortunately, techniques used successfully to superovulate ruminants, such as administration of porcine follicle stimulating hormone and equine chorionic gonadotropin have little effect in the mare. [4 and 5]The most consistent therapy used to induce multiple ovulations in mares has been administration of purified equine pituitary gonadotropins. Equine pituitary extract (EPE) is a purified gonadotropin preparation containing approximately 6% to 10% LH and 2% to 4% FSH.[6] EPE has been used for many years to induce multiple ovulations in mares [7, 8 and 9] and increase the embryo recovery rate from embryo transfer donor mares. [10] Recently, a highly purified equine FSH product has become available commercially.The objectives of this study were to evaluate the efficacy of purified eFSH in inducing superovulation in cycling mares and to determine the relationship between ovulation rate and pregnancy rate or embryo collection rate in superovulated mares.

Materials and methods

Experiment 1

Forty-nine normally cycling mares, ranging in age from 3 to 12 years, were used in a study at Colorado State University. Group 1 (control) mares (n = 29) were examined daily when in estrus by transrectal ultrasonography. Mares were administered an implant containing 2.1 mg deslorelin (Ovuplant, Ft. Dodge Animal Health, Ft. Dodge, IA) subcutaneously in the vulva when a follicle 35 mm in diameter was detected. Mares were bred with frozen semen (800 million spermatozoa; minimum of 30% progressive motility) from 1 of 4 stallions 33 and 48 hours after deslorelin administration. The deslorelin implants were removed after detection of ovulation.[11] Pregnancy status was determined at 14 and 16 days after ovulation.Group 2 mares (n = 10) were administered 25 mg of eFSH (Bioniche Animal Health USA, Inc., Athens, GA) intramuscularly twice daily beginning 5 or 6 days after ovulation was detected. Mares received 250 g cloprostenol (Estrumate, Schering-Plough Animal Health, Omaha, NE) intramuscularly on the second day of eFSH treatment. Administration of eFSH continued until a majority of follicles reached a diameter of 35 mm, at which time a deslorelin implant was administered. Mares were subsequently bred with the same frozen semen used for control mares, and pregnancy examinations were performed as described above.Group 3 mares (n = 10) received 12 mg of eFSH twice daily starting 5 or 6 days after ovulation and were administered 250 μg cloprostenol on the second day of treatment. Mares were randomly selected to receive either a deslorelin implant (n = 5) or 2500 IU of human chorionic gonadotropin (hCG) intravenously (n = 5) to induce ovulation when a majority of follicles reached a diameter of 35 mm. Mares were bred with frozen semen and examined for pregnancy as described above.

Experiment 2

Sixteen cycling light-horse mares were used during the physiologic breeding season in Brazil. Reproductive activity was monitored by transrectal palpation and ultrasonography every 3 days during diestrus and daily during estrus. On the first cycle, mares were administered 2500 IU hCG intravenously once a follicle 35 mm was detected. Mares were subsequently inseminated with pooled fresh semen from 2 stallions (1 billion motile sperm) daily until ovulation was detected. An embryo collection procedure was performed 7 days after ovulation. Mares were subsequently administered cloprostenol, and eFSH treatment was initiated. Mares received 12 mg eFSH twice daily until a majority of follicles were 35 mm in diameter, at which time hCG was administered. Mares were inseminated and embryo collection attempts were performed as described previously.

Statistical analysis

In experiment 1, 1-way analysis of variance with F protected LSD was used to analyze quantitative data. Pregnancies per ovulation were analyzed by x2 analysis. In experiment 2, number of large follicles, ovulation rate, and embryo recovery rate were compared by Student,'s t-test. Data are presented as the mean S.E.M. Differences were considered to be statistically significant at p < .05, unless otherwise indicated.

Results

In experiment 1, mares treated with 25 mg eFSH twice daily developed a greater number of follicles 35 mm in diameter (p = .001) and ovulated a greater number of follicles (p = .003) than control mares (Table 1). However, the number of pregnancies obtained per mare was not significantly different between the control group and the group receiving 25 mg eFSH (p = .9518). Mares treated with 12 mg eFSH and administered either hCG or deslorelin to induce ovulation also developed more follicles 35 mm (p = .0016 and .0003, respectively) than untreated controls. Mares receiving eFSH followed by hCG ovulated a greater number of follicles (p = .003) than control mares, whereas the number of ovulations for mares receiving eFSH followed by deslorelin was similar to that of control mares (p = .3463). Pregnancy rate for mares induced to ovulate with hCG was higher (p = .0119) than that of control mares, whereas the pregnancy rate for eFSH-treated mares induced to ovulate with deslorelin did not differ from that of controls (p = .692). Pregnancy rate per ovulation was not significantly different between control mares (54.5%) and mares treated with eFSH followed by hCG (52.9%). The lowest pregnancy rate per ovulation was for mares stimulated with 25 mg eFSH and induced to ovulate with deslorelin. The mean number of days mares were treated with 25 mg or 12 mg of eFSH was 7.8 ± 0.4 and 7.5 ± 0.5 days, respectively. Overall, 80.0% of mares administered eFSH had multiple ovulations compared with 10.3% of control mares.  相似文献   

3.
Sixty nonlactating light-horse mares were used to compare the efficacy of hCG, buserelin (a GnRH analog) and luprostiol (a PGF2α analog) for induction of ovulation in cycling mares. Mares were assigned to 1 of 4 treatments: 1) controls; 2) 40 μg buserelin IM at 12 hr intervals during estrus until ovulation; 3) 7.5 mg IM luprostiol; and 4) 3,300 IU hCG. Treatments were given once a mare obtained a ≥35mm follicle and had been in estrus ≥2 days. Both buserelin and hCG shortened (p<0.05) the interval from treatment to ovulation compared to controls; whereas, luprostiol failed to hasten ovulation. Number of follicles ovulated was similar among all 4 groups. Although buserelin and hCG were equal in their ability to induce ovulation, an average of 3.8 injections of buserelin was required for hastening of ovulation.  相似文献   

4.
This study investigated the efficacy of two dosage regimens of a potent GnRH analogue (GnRHa), deslorelin acetate, in inducing ovulation in seasonally anestrous mares. Forty-five seasonally anestrous mares were randomly assigned according to follicular size to one of three treatment groups: control, increasing GnRHa dose, and constant GnRHa dose. Treatment began on February 28 and continued until ovulation or for a maximum of seven treatments. Mares were palpated every other day until a 35 mm follicle was detected, then every day until ovulation or regression of the follicle occurred. Blood samples were taken from five randomly chosen mares in each treatment group and analyzed for LH levels.Twenty percent of mares in both deslorelin treatment groups ovulated, while no control mares ovulated during the treatment period. There was no difference in the number of mares that ovulated between treatment groups. Four of the six mares that ovulated were in transitional anestrus at the initiation of treatment, while only two were in deep anestrus.Concentrations of LH were greater (p=0.0008) in both GnRH-treated groups than in the control mares. Concentrations of LH did not differ between the two GnRH-treated groups until day 12 of treatment, when mares treated with a constant dosage had higher (p=0.0358) levels of LH than those treated with an increasing dosage. It is possible that administration of larger amounts of the GnRH agonist lowered the sensitivity of the pituitary to stimulation by GnRH.Deslorelin acetate did stimulate follicular growth and ovulation in a limited number of anestrous mares. Further investigation into the potential of this short-term implant to shorten the onsent of the breeding season is recommended.  相似文献   

5.
Early pregnancy loss in the mare is a major cause of infertility and economic loss. To study this important problem, sequential ultrasound examinations were completed on breeding farm mares (n = 404 pregnancies). The incidence of pregnancy loss between Week 2 and Week 8 post ovulation was 42 losses out of 404 pregnancies.(10.4%) More (p<0.05) pregnancies were lost at 2–4 weeks post ovulation than at 4–6 or 6–8 weeks post ovulation (23/42 vs 9/42 or 10/42). The number of days from detection of pregnancy loss until the subsequent ovulation was higher (p<0.01) for mares in which pregnancy loss was detected at 6–8 weeks post ovulation than for mares in which pregnancy loss was detected at 2–4or 4–6 weeks post ovulation (21.1 ± 3.90 days vs 12.7 ± 1.59 or 9.5 ± 1.05 days,respectively). Thirty-one of 45 mares which lost pregnancies were again bred. Sixty-five percent (20/31) of these mares again became detectably pregnant but forty percent (8/20) of thesepregnancies were subsequently lost.  相似文献   

6.
Horse owners want to have their mares bred as early as possible in the breeding season after February 1. Numerous medical treatments, such as progesterone, dopamine antagonists, and gonadotropin-releasing hormone have been administered to anestrous or transitional mares in an attempt to induce follicular development. Some of these treatments are ineffective or impractical, so there is a need in the horse industry to develop alternative techniques to stimulate follicular development and ovulation early in the breeding season. Twenty transitional mares were assigned to one of two treatment groups. Mares in group 1 (n = 10) served as untreated controls, and mares in group 2 (n = 10) were administered 12.5 mg of purified equine follicle-stimulating hormone (eFSH) (Bioniche Animal Health USA, Inc., Athens, Ga) intramuscularly twice daily for a maximum of 15 consecutive days. Mares were considered to be in transition when the diameter of the largest follicle was ≥25 mm. Once one or more follicles >35 mm were detected, eFSH treatment was discontinued and human chorionic gonadotropin was administered intravenously. The percentage of mares ovulating during the 15-day observation period was compared by means of chi-square analysis. The interval to ovulation and the number of ovulations per mare were compared between the two groups by Student t test. In 8 of 10 mares treated with eFSH follicles developed and ovulation occurred during the 15-day observation period, compared with 0 of 10 control mares. Interval from onset of treatment to ovulation was 7.6 ± 2.4 days for these eight mares. The eight mares were treated for an average of 5.2 ± 1.3 days with eFSH. Thus, the eFSH treatment was effective in advancing the first ovulation of the year in transitional mares.  相似文献   

7.
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   

8.
Soon after Ovuplant™, the sustained-release implant containing the gonadotropin releasing hormone (GnRH) agonist deslorelin, was approved for commercial use in the United States for induction of ovulation in mares, anecdotal field observations were reported that some Ovuplant™—treated mares that did not become pregnant experienced a delayed return to estrus and prolonged inter-ovulatory interval. Although those observations have been subsequently confirmed, further data on how mares respond to Ovuplant™ compared to human chorionic gonadotropin (hCG) during the post-treatment period is needed. The objective of this study was to further evaluate the clinical use of Ovuplant™ by comparing the reproductive performance of commercial broodmares treated with hCG or Ovuplant™. This retrospective study was completed by examining the 1999 reproductive records of 106 mares treated with hCG during 134 estrous cycles and 117 mares treated with Ovuplant™ during 151 estrous cycles. There were no differences (P > 0.10) in follicle size at the time of treatment (39.4 ± 0.5 vs. 38.9 ± 0.5 mm), interval from treatment to ovulation (2.2 ± 0.1 vs. 2.2 ± 0.1 days), proportion of mares that failed to ovulate after treatment (3.0 vs. 4.6 %), or per-cycle pregnancy rate (47.7 vs. 51.4 %) between hCG-and Ovuplant™-treated mares, respectively. The interval from ovulation to return to estrus (25.8 ± 1.3 vs. 15.5 ± 0.6 days) and the inter-ovulatory interval (30.4 ± 1.5 vs. 20.8 ± 0.6 days) were longer (P<0.001) for Ovuplant™-compared to hCG-treated mares, and the proportion of non-pregnant mares that failed to return to estrus within 30 days after ovulation (31.4 vs. 1.5 %) was higher (P<0.001) for Ovuplant™-compared to hCG-treated mares, respectively. For Ovuplant™—treated mares, follicle size at the time of treatment tended (P<0.1) to be smaller for mares that failed to return to estrus within 30 days compared to mares that returned to estrus within 30 days (37.1 ± 1.1 vs. 40.1 ± 0.6 mm, respectively). Also, the average date of ovulation during the calendar year was later (P < 0.05) for Ovuplant™—treated mares that failed to return to estrus within 30 days compared to those that returned to estrus within 30 days (May 15 ± 4 vs. April 30 ± 4 days). The results of this study confirm previous reports that although the ovulatory response and fertility were not different for hCG- and Ovuplant™—treated mares, mares treated with Ovuplant™ that did not become pregnant had a significantly delayed return to estrus and prolonged inter-ovulatory interval. Based on recently published information, it appears this effect is due to Ovuplant™—induced down-regulation of the pituitary gland, which suppresses subsequent follicular growth and development. This study also demonstrated that follicle size and/or season may influence the probability that Ovuplant™—treated mares would experience a delayed return to estrus/ovulation; therefore, further work is needed to determine whether these or other factors are related to this specific outcome following Ovuplant™—treatment.  相似文献   

9.
The objective of this study was to evaluate various equine follicle-stimulating hormone (eFSH) treatment protocols and the effect of “follicle coasting” on ovulation and embryo recovery rates in mares. Cycling mares (n = 40) were randomly assigned to one of four groups 7 days after ovulation: (1) 12.5 mg eFSH twice daily until follicles were 35 mm or larger; (2) 12.5 mg eFSH twice daily until follicles were 32 mm or larger; (3) 12.5 mg eFSH twice daily for 3.5 days followed by 12.5 mg eFSH enriched with luteinizing hormone (LH) twice daily until follicles were 35 mm or larger; and (4) 25 mg eFSH once daily until follicles were 32 mm or larger. Mares in groups 1 and 3 were injected with human chorionic gonadotropin (hCG) (2500 IU intravenously) at the end of eFSH treatment, whereas mares in groups 2 and 4 were given hCG approximately 42 and 54 hours, respectively, after the last eFSH treatment (“follicle coasting”). Nonsurgical embryo collection was performed 6.5 to 7.5 days after ovulation. Each mare experienced a nontreated estrous cycle before being reassigned to a second treatment. Ovulation rates for mares in treatment groups 1 to 4 were 3.3 ± 0.4, 4.1 ± 0.4, 3.5 ± 0.4, and 2.8 ± 0.4 (mean ± SEM; P < .05), respectively. One or more embryos were recovered from more than 80% of mares in each treatment group, and embryo recovery rate per flush was similar among treatment groups (1.9 ± 0.3, 2.6 ± 0.3, 1.9 ± 0.3 and 1.9 ± 0.3, respectively; P > .05). The overall embryo recovery rate was 2.1 ± 1.5 embryos per flush. In summary, ovulation rate was higher for mares treated with eFSH (3.4 ± 0.4) compared with non-treated controls (1.1 ± 0.2). Ovulation rate in mares in which hCG was delayed (follicle coasting) was higher (P < .05) when treatments were given twice per day versus once per day. Administration of equine luteinizing hormone (eLH) in conjunction with eFSH did not have an advantage over mares treated only with eFSH.  相似文献   

10.
In a blinded trial, the effectiveness and safety of 2.2 mg of the GnRH analog deslorelin acetate, administered in a short–term implant (STI) to normally cycling mares in estrus with a dominant ovarian follicle of 30 mm in diameter or larger, were evaluated, using a placebo implant as a negative control. A total of 39 mares received treatments at admittance with pre–randomized implants containing either 2.2 mg or 0 mg deslorelin. Mares were teased daily and examined rectally with ultrasound at 24 h intervals to determine time to Ovulation and duration of estrus. The number of breedings and the pregnancy rate at 18 (±3) and 38 (±3) days were recorded, as were systemic side effects and local reactions at the implantation sites. Pregnancies resulting from breedings during the treatment estrus and/or from breedings during the next estrus were followed and the early and late pregnancy loss rate, the number of pregnancies going to term and of live–born foals was recorded.Mean follicle diameter at treatment was not significantly different between the deslorelin and placebo treatment group with 41.6 mm and 40.8 mm, respectively. Treatment with deslorelin STI reduced the time interval to Ovulation significantly from 69.5±25.48 h to 42.7±12.35 h (p<0.001). The percentage of mares having ovulated within 48 h rose from 26.3% to 95.0%, respectively, for placebo and deslorelin STI (p<0.001). As a consequence, the duration of estrus in days and the percent of animals requiring more than 1 breeding were significantly reduced in deslorelin treated animals from 5.4 days to 4.6 days, and from 55.6% to 5.0%, respectively (p=0.009 and =0.001). The percent of mares pregnant from breedings at the treatment estrus (65.0% versus 44.4%) or the next estrus (83.3% versus 92.3%) was satisfactory and similar for deslorelin and placebo treated mares (p>0.005), and in 70.0% and 66.7% of these once or twice bred mares did pregnancies go to term and live foals were born. kw|Keywords|k]GnRH  相似文献   

11.
The use of equine FSH (eFSH) for inducing follicular development and ovulation in transitional mares was evaluated. Twenty-seven mares, from 3 to 15 years of age, were examined during the months of August and September 2004, in Brazil. Ultrasound evaluations were performed during 2 weeks before the start of the experiment to confirm transitional characteristics (no follicles larger than 25 mm and no corpus luteum [CL] present). After this period, as the mares obtained a follicle of at least 25 mm, they were assigned to one of two groups: (1) control group, untreated; (2) treated with 12.5 mg eFSH, 2 times per day, until at least half of all follicles larger than 30 mm had reached 35 mm. Follicular activity of all mares was monitored. When most of the follicles from treated mares and a single follicle from control mares acquired a preovulatory size (≥35 mm), 2,500 IU human chorionic gonadotropin (hCG) was administered IV to induce ovulation. After hCG administration, the mares were inseminated with fresh semen every other day until ovulation. Ultrasound examinations continued until detection of the last ovulation, and embryo recovery was performed 7 to 8 days after ovulation. The mares of the treated group reached the first preovulatory follicle (4.1 ± 1.0 vs 14.9 ± 10.8 days) and ovulated before untreated mares (6.6 ± 1.2 vs 18.0 ± 11.1 days; P < .05). All mares were treated with prostaglandin F2α (PGF2α), on the day of embryo flushing. Three superovulated mares did not cycle immediately after PGF2α treatment, and consequently had a longer interovulatory interval (22.4 vs 10.9 days, P < 0.05). The mean period of treatment was 4.79 ± 1.07 days and 85.71% of mares had multiple ovulations. The number of ovulations (5.6 vs 1.0) and embryos (2.0 vs 0.7) per mare were higher (P < 0.05) for treated mares than control mares. In conclusion, treatment with eFSH was effective in hastening the onset of the breeding season, inducing multiple ovulations, and increasing embryo production in transitional mares. This is the first report showing the use of FSH treatment to recover embryos from the first cycle of the year.  相似文献   

12.
The present experiment characterized the pituitary responsiveness to exogenous GnRH in the first 10 d after ovulation following commercially available deslorelin acetate implantation at the normal dosage for hastening ovulation in mares. Twelve mature, cyclic mares were assessed daily for estrus and three times weekly for ovarian activity starting May 1. Mares achieving a follicle at least 25 mm in diameter or showing signs of estrus were checked daily thereafter for ovarian characteristics. When a follicle >30 mm was detected, mares were administered either a single deslorelin acetate implant or a sham injection and then assessed daily for ovulation. On d 1, 4, 7, and 10 following ovulation, each mare was challenged i.v. with 50 microg GnRH, and blood samples were collected to characterize the LH and FSH responses. The size of the largest follicle on the day of treatment did not differ (P = 0.89) between groups. The number of days from treatment to ovulation was shorter (P < 0.001) by 2.0 d for the treated mares indicating a hastening of ovulation. The size of the largest follicle present on the days of GnRH challenge was larger in the treated mares on d 1 (P = 0.007) but smaller on d 10 (P = 0.02). In addition, the interovulatory interval was longer (P = 0.036) in the treated mares relative to controls by 4.4 d. Concentrations of FSH in plasma of the treated mares were lower (P < 0.05) than control concentrations from d 3 to 12; LH concentrations in the treated mares were lower (P < 0.05) relative to controls on d 0 to 5, d 7, and again on d 20 to 23. Progesterone values were the same (P = 0.99) for both groups from 2 d before ovulation though d 23. There was an interaction of treatment, day, and time of sampling (P < 0.001) for LH and FSH concentrations after injection of GnRH. Both the LH and FSH responses were suppressed (P < 0.009) in the treated mares relative to controls on d 1, 4, and 7; by d 10, the responses of the two groups were equivalent. In conclusion, deslorelin administration in this manner increased the interovulatory interval, consistently suppressed plasma LH and FSH concentrations, and resulted in a complete lack of responsiveness of LH and FSH to GnRH stimulation at the dose used during the first 7 d after the induced ovulation. Together, these results are consistent with a temporary down-regulation of the pituitary gland in response to deslorelin administered in this manner.  相似文献   

13.
Anterior pituitary gland contents of LH and LHß- and α-subunit mRNAs, and circulating concentrations of LH and testosterone, were determined in bulls treated with the LH-releasing hormone (LHRH) agonist deslorelin. Brahman (Bos indicus) bulls (14-month-old) were allocated to two groups and received the following: Control (n = 5), no treatment; Deslorelin (n = 4), four deslorelin implants (approximately 200 μg total deslorelin/day) for 36 d. Plasma concentrations of LH were higher in bulls treated with deslorelin on Day 1, had returned to typical levels by Day 8, and did not differ for control bulls and bulls treated with deslorelin from Day 8 to Day 29. Pituitary content of LH on Day 36 was reduced (P < 0.001) in bulls treated with deslorelin (33 ± 4 ng/mg) compared with control bulls (553 ± 142 ng/mg). Relative pituitary content of LHß-subunit mRNA was also reduced on Day 36 in bulls treated with deslorelin (Control, 0.65 ± 0.10; Deslorelin, 0.22 ± 0.04; P = 0.003). However, α-subunit mRNA relative content did not differ (Control, 0.73 ± 0.15; Deslorelin, 1.06 ± 0.12; P > 0.05). Plasma concentrations of testosterone were increased over the period of the experiment in the bulls treated with deslorelin compared with control bulls. This is the first demonstration of reduced pituitary content of LHß-subunit mRNA and LH, and unaltered content of α-subunit mRNA, in bulls treated with LHRH agonist. This was associated with apparently typical plasma concentrations of LH and elevated plasma testosterone. The anterior pituitary in bulls treated with LHRH agonist, therefore, undergoes classical desensitization and downregulation, but plasma LH and testosterone are not suppressed.  相似文献   

14.
The efficacy of melengestrol acetate (MGA) to shorten the vernal transition of mares by synchronising and accelerating the first ovulation of the year after 60 days of phototherapy was determined by ultrasonographic monitoring. Sixteen mares in late transition were fed two doses of MGA (150 mg/mare/day and 100 mg/mare/day, respectively) for 10 days. A luteolytic dose of prostaglandin was administered to each mare one day after the end of MGA treatment. The presence and duration of oestrus, follicular growth, uterine oedema and presence of ovulation were monitored by ultrasonography and the cervical tone was evaluated by rectal palpation. Ovulation was detected in 87.5% of the mares treated with 150 mg MGA/mare/day for 10 days, and in 62.5% of the mares receiving 100 mg MGA/mare/day for 10 days. This was statistically different (P = 0.03) from the untreated control mares having an ovulation rate of 20%. Mares that received 150 mg MGA/day for 10 days had a mean treatment to ovulation interval of 13.1 +/- 5.97 days after the end of treatment, while mares that received 100 mg MGA/day for 10 days had a mean of 25.6 +/- 10.50 days (P = 0.01) to ovulation. These results suggest that MGA can be used for synchronising and hastening the first ovulation of the year in mares.  相似文献   

15.
The objective of this study was to compare the rate of ovulation when deslorelin and/or human chorionic gonadotropin (hCG) was administered in mares in both the transition period and the ovulatory season. A total of 200 Paint Horses, Quarter Horses, and crossbred mares were used during the transition season (July to September) and the ovulatory season (October to February) of the southern hemisphere. The animals were divided into four groups. In the control group (n = 72), mares received 1 mL of saline; in deslorelin group (n = 171), 1.5 mg of deslorelin was administered by intramuscular (IM) injection; in hCG group (n = 57), 1,667 IU of hCG was administered IV; and in hCG + deslorelin group (n = 438), 1.5 mg of deslorelin (IM) and 1,667 IU of hCG (IV) were administered. The drugs were administered after follicles ≥35 mm in diameter were identified and grade III uterine edema was observed. At 48 hours after application, ultrasonography was performed to detect ovulation. During the transition period, the ovulation rates were 4.3% (control), 78.6% (deslorelin), 50% (hCG), and 73.3% (hCG + deslorelin). During ovulatory season, the ovulation rates were 16.4% (control), 68.8% (deslorelin), 60% (hCG), and 73% (hCG + deslorelin). There was no significant difference (P > .05) in the ovulation rate between the groups or the periods, except that the control group was lower than all others. Furthermore, both hCG and deslorelin are viable options for inducing ovulation during the transition period before ovulation season.  相似文献   

16.
Deslorelin acetate implants, recently licensed in Ireland and the UK for ovulation induction in mares, have been associated with prolonged interovulatory intervals in USA studies, leading to the practice of removing implants postovulation. Trial data in Australia indicate a less pronounced effect on interovulatory intervals, suggesting possible geographical variation. Objectives of the current study were to assess the effect of deslorelin implants, with and without removal on oestrous cycle length in Irish- and UK-based Thoroughbred broodmares. Data were collected retrospectively from 88 oestrous cycles. A statistically significant difference (P=0.02) was found between interovulatory intervals in mares in which the deslorelin implant was not removed, compared with administration and removal of the implant or the use of human chorionic gonadotrophin. The results suggest that implant removal when possible is advisable. The delay in subsequent ovulations was less marked than that reported in some studies from the USA. This information is useful in deciding when to schedule subsequent breeding for mares which received a deslorelin implant during the previous oestrous period and provides evidence to counter-concerns that mares treated with deslorelin implants may experience a long delay in return to oestrus if the implant is not removed.  相似文献   

17.
Stallion-like sexual behavior in mares is rare, except in association with ovarian tumors or hormonal treatments. The rarity of the phenomenon was confirmed in a recent 3-year study. The mean number of mares with detected stallion-like behavior, including mounting with thrusts, during an entire ovulatory season was 5.7 (17/3 years) in a herd averaging 105 mares (5% incidence/mare/season). From a total of 17 mountings of an estrous mare by another mare, 15 occurred when the mounting mare was in the follicular phase and two when in the early luteal phase. Plasma testosterone concentration on the day of mounting was higher (P < 0.01) in the mounting mares (17.7 ± 2.3 pg/ml) than in the standing mares (10.9 ± 0.5 pg/ml). No other deviation in the endocrine, behavioral, or morphologic aspects of the estrous cycle was observed. In another study, testosterone was assayed daily from 7 days before to 4 days after ovulation in seven mares during estrous cycles with no detected mare-on-mare mountings. Concentrations during the follicular phase were highest on the days corresponding to when mare-on-mare mounting was detected in the previous study. It is concluded that the rare occurrence of stallion behavior by untreated mares with no detected ovarian tumors is a consequence of an unusually high, apparently transient fluctuation in circulating testosterone at the time of mounting.  相似文献   

18.
OBJECTIVE: To characterize the temporality of dates of breeding and abortion classified as mare reproductive loss syndrome (MRLS) among mares with abortions during early gestation. ANIMALS: 2,314 mares confirmed pregnant at approximately 28 days after breeding from 36 farms in central Kentucky, including 515 mares that had early-term abortions. PROCEDURE: Farm veterinarians and managers were interviewed to obtain data for each mare that was known to be pregnant to determine pregnancy status, breeding date, last date known to be pregnant, and date of abortion. RESULTS: Mares bred prior to April 1, 2001, appeared to be at greatest risk of early-term abortion, both among and within individual farms. Mares bred in mid-February appeared to be at greatest risk of abortion, with an estimated weekly incidence rate of abortion of 66% (95% CI, 52% to 80%). CONCLUSIONS AND CLINICAL RELEVANCE: Mares in central Kentucky bred between mid-February and early March were observed to be at greatest risk of early-term abortion, and risk gradually decreased to a background incidence of abortion of approximately 11%. Mares bred after April 1, 2001, appeared to be at markedly less risk, indicating that exposure to the cause of MRLS likely occurred prior to this date.  相似文献   

19.
Over four years, four investigators in the Northern Hemisphere treated 413 privately owned transition phase mares between late February and early April, for the purpose of breeding such mares early in the season. Mares received an intravaginal device (CIDR-B) carrying 1.9 g progesterone, for about 12 days. Thereafter mares forming preovulatory follicles >30 mm were either treated with a short acting implant releasing the GnRH analog deslorelin (Ovuplant™) or with 1,500—2,500 IU hCG, or not. Follicle sizes were determined with ultrasonography at admission to the study (i.e. day of CIDR-B insertion), at intervals during treatment, at device removal and in 24 (to 48) hour intervals thereafter to determine the time for treatment to induce and accelerate ovulation and to ovulation, respectively. Pregnancies were determined by ultra-sonography between Days 14 to 18 after breeding, mostly 12 to 14 days after ovulation. Based on the size of the largest follicle at admission, mares were grouped into Classes with a ollicle diameter of 10 mm or less in Class I, and mares with follicles 11-20 mm, 21-30 mm and >30 mm in Classes II, III and IV, respectively. Overall, 80.2% of all mares responded to treatment with estrus and 80.7% ovulated. For mares in Classes I to IV, the rate of mares bred and becoming pregnant was 53.4% and 66.7%, 65.6% and 58.7%, 87.5% and 52.3%, and 75.0% and 52.0%, respectively. The overall pregnancy rate was 55.6% for the first breeding in response to treatment. Mares not assisted with Ovuplant or hCG were bred at a significantly lower rate (<0.0001) and the pregnancy rate was lower, 44.4% vs. 54.2% and 60.5%, respectively. Treatments with Ovuplant or hCG ensured ovulation rates of 96.0 and 84.9% versus 53.3% in unassisted mares overall. Follicle diameters increased significantly with CIDR-B in situ, and progressed after device removal to >30 mm within 4.0 days and to ovulation 5.3 days. Those mares in Class I responding to treatment (ca 60%) did not differ from Class II to IV mares in almost all the parameter evaluated. Significant differences were seen in the UK in response to treatment between years for the percentage of mares showing heat, ovulated, were bred and became pregnant.  相似文献   

20.
The aim of the present study, was to evaluate whether a single subcutaneous administration of the GnRH analogue buserelin could induce ovulation in the mare during the breeding season. Two studies were carried out under field conditions. In Experiment 1, 90 cycles of trotter mares aged 2-7 years, were assigned to a buserelin group (Bus1) or to a control group (Control), in the presence of a >/=35 mm pre-ovulatory follicle, with uterine oedema and a relaxed cervix. Ten mares were assigned to the two groups for 32 cycles in Bus1 and 52 cycles in Control, two mares received only Bus1 for three cycles, and one mare was assigned to Control for three cycles. Mares treated with buserelin received 6 ml of SUPREFACT s.c. (1.05 mg/ml buserelin acetate), and no treatment was given in Control. The ovulation rate between 24 and 48 h was higher (p < 0.0001) in Bus1 (31/35) than in Control (15/55). In Experiment 2, the condition of inducing ovulation with 6 ml SUPREFACT s.c. (Bus2) or 1500 ui human chorionic gonadotropin were identical to the first study. Forty-nine mares of ages 2-21 years, were used for 120 cycles, 56 cycles were assigned to Bus2, and 64 cycles were induced with 1500 IU human chorionic gonadotropin i.v. No significant difference was found in the ovulation rate on day 2 (38/56, 50/64), or in the fertility rate (19/48, 26/57). No negative effect of the treatment was observed with repeated buserelin administration in either study during the breeding season. We can conclude that a single administration of buserelin induces ovulation in the mare, under suitable conditions for veterinary practitioners.  相似文献   

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