Changes in plasma progesterone concentrations in mares treated with cloprostenol and human chorionic gonadotropin and inseminated during estrus

Daily changes in the plasma progesterone concentrations were determined in eight mares treated with intramuscular injections of 250 μg cloprostenol, a prostaglandin analogue, followed five days later by 2500 I.U. human chorionic gonadotropin. A second cloprostenol injection was given 14 days after the first; the mares were then inseminated on the third and fifth day of the subsequent estrus and a second injection of human chorionic gonadotropin was administered on the fifth day. The onset of estrus following the second cloprostenol treatment was synchronized beginning three to four days after treatment in all eight mares. All eight ovulated, five mares conceived and only four foaled. Evaluation of the progesterone profiles provided reliable indicators of luteolysis, ovulation and luteal function. Decreasing plasma progesterone concentrations were associated with cloprostenol induced luteolysis or preceded spontaneous onset of estrus. The plasma progesterone concentrations increased consistently after ovulation, and in the pregnant mares, the progesterone concentrations remained high during the first month after insemination.     

鲁中肉羊育种中FecB突变应用效果分析

为评价FecB突变在鲁中肉羊培育中的应用效果,本研究首先利用TaqMan探针高通量分型技术对2295只鲁中肉羊FecB基因进行分型,统计FecB基因在鲁中肉羊群体中的分布情况,然后结合253只母羊的产羔数据和865只初生羔羊、83只3月龄母羔羊的体尺体重数据分析FecB基因对鲁中肉羊产羔数和早期生长发育的影响。群体遗传学分析表明:鲁中肉羊群体存在AA(++)、AG(B+)和GG(BB)3种FecB基因型,在新品种培育过程中突变纯合子频率逐年增加,且表现为中度多态性(0.25<多态信息含量<0.5);卡方适合性检验发现,FecB突变位点向Hardy-Weinberg平衡状态(P>0.05)转变;BB型母羊平均产羔数高于++型(P<0.01);BB型初生羔羊的体重低于++型(P<0.01),BB型初生公羔的体高、胸围、胸宽、胸深和初生母羔的胸深和管围低于++型(P<0.05),B+型3月龄母羔的管围低于++型(P<0.05)。结果显示,FecB突变显著提高了鲁中肉羊的产羔数,但对初生羔羊的生长发育存在一定的逆增长效应。     

Kisspeptins and the reproductive axis: potential applications to manage reproduction in farm animals

Kisspeptins (Kp) are a family of neuropeptides produced mainly by two hypothalamic neuronal cell populations. They have recently emerged as a major regulator of the gonadotropin axis and their action is located upstream of the gonadotropin-releasing hormone (GnRH) cell population. In less than 10 yr a growing body of literature has demonstrated the involvement of these peptides in most, if not all, aspects of reproductive axis maturation and function. In contrast to these abundant basic research studies, few experiments have evaluated the potential application of Kp as tools to manipulate reproduction in domestic animals. In mammals, exogenous Kp administration potently stimulates gonadotropin secretion. This action is exerted mainly, if not exclusively, through the stimulation of GnRH release. Intravenous, intraperitoneal, or subcutaneous administration of Kp induced a robust and rapid increase in plasma gonadotropins (luteinizing hormone [LH] and follicle-stimulating hormone [FSH]). However, this stimulatory effect is of short duration. Prolonged LH and FSH release over several hours can be achieved only when Kp are given as repeated multiple bolus or as an infusion. Kp administration was used in two experimental models, ewe and pony mare, with the aim of inducing well-timed and synchronized ovulations. During the breeding season, progesterone-synchronized ewes were given an intravenous infusion of Kp starting 30 h after the removal of progesterone implants. An LH surge was induced in all Kp-treated animals within 2 h of infusion onset. In contrast, in pony mares a constant infusion of Kp for 3 d in the the late follicular phase was unable to induce synchronized ovulation. Another set of studies showed that Kp could be used to activate reproductive function in acyclic animals. Pulsatile administration of Kp in prepubertal ewe lambs was shown to activate ovarian function, leading to enhanced ovarian steroidogenesis, stimulation of LH preovulatory surge, and ovulation. In anestrous ewes, an intravenous infusion of a low dose of Kp induced an immediate and sustained release of gonadotropins, followed a few hours later by an LH surge. This hormonal pattern mimicked hormonal changes normally observed during the estrous cycle follicular phase and was associated with a high percentage of ovulating animals (80%). In summary, exogenous administration of Kp appears to be a new tool to manipulate reproduction. However, optimal doses and periods of treatment should be defined for each species, and the development of powerful analogs or long-term release formulations is necessary before large-scale applications in domestic animals could be envisaged.     

Use of a GnRH antagonist,antarelix, associated or not with hCG,to control ovulation in cyclic pony mares

The GnRH antagonist antarelix (Teverelix™) was administered to mares (0.01 mg/kg, i.v., twice a day) during the periovulatory period. In Experiment 1, 20 mares were divided into a treated (A3d−) and a control (Control−) group. A3d− mares received antarelix for 3 days from the day when the dominant follicle (F1) reached 32 mm (D0). In Experiment 2, 10 mares were divided into a treated (A6d+) and a control (Control+) group. A6d+ mares received antarelix for 6 days from D0 and hCG was injected in all animals (1600 IU, i.v.) on D1. Pregnancies were determined 13 days after ovulation. In both experiments, antarelix interrupted or totally abolished the LH surge. In Experiment 1, 5/10 of the A3d− mares (with maximum LH concentrations of 11.6 ng/ml at the beginning of treatment) ovulated at the same time as the Control− mares; the other five mares (with LH concentrations under 5.4 ng/ml) ovulated 13.4±0.6 days later. In Experiment 2, all the A6d+ mares ovulated at the same time as the Control+ mares. In treated mares which ovulated during the treatment, progesterone concentrations and fertility did not differ from control mares. These results demonstrate that in mares: (1) a small elevation of endogenous LH can induce ovulation, (2) ovulation can be postponed approximately 13 days after a 3-day antarelix treatment if initiated just before the preovulatory LH surge, (3) ovulation can be induced by hCG on depressed levels of endogenous LH, (4) the inhibition of the post ovulatory LH surge has no effect either on the corpus luteum or on fertility.     

Comparison of two dosage regimens of the GNRH agonist deslorelin acetate on inducing ovulation in seasonally anestrous mares

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.     

Effects of gonadotropin-releasing hormone infused in a pulsatile or continuous fashion on serum gonadotropin concentrations and ovulation in the mare.

Studies were conducted to compare continuous vs pulsatile i.v. infusion of GnRH on serum gonadotropin concentrations and ovulation in seasonally anestrous mares and in cycling mares. Anestrous mares (Exp. 1) received no treatment (control; n = 3), 2, or 20 micrograms of GnRH/h continuous infusion (CI) (n = 4 and n = 6, respectively), or 20 micrograms of GnRH/h pulsatile infusion (PI) (n = 5). After initiation of GnRH infusion, serum LH levels increased earlier, and to a greater extent, in the PI group than in other groups (P less than .05). In contrast, serum FSH concentrations did not differ among groups. The number of days to development of the first 35-mm follicle was not different among GnRH treatment groups; however, mares receiving PI ovulated on d 9.4 of treatment, 2.8 d earlier than those receiving 20 micrograms of GnRH/h CI (P less than .05). Mares given 2 micrograms of GnRH/h CI failed to ovulate spontaneously after 16 d of treatment, but each one ovulated within 2 to 4 d after injection of 2,000 IU of hCG on d 16. Control mares did not ovulate or show any significant follicular development throughout the experiment. Cycling mares (Exp. 2) received no treatment (control; n = 6), 20 micrograms of GnRH/h CI, or 20 micrograms of GnRH/h PI (n = 4) beginning on d 16 of an estrous cycle (d 0 = day of ovulation). Serum LH concentrations in all groups increased after initiation of treatment; however, on the day of ovulation LH concentrations were lower in the CI group than in the PI or control groups (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Efficacy of Deslorelin Acetate (SucroMate) on Induction of Ovulation in American Quarter Horse Mares

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.     

Orientation studies of ovulation release in mice to test gonadotropic preparations. 2. FSH, PMSG and Gn-RH activity

The doses of FSH (follicle-stimulating hormone), PMSG (pregnant mare serum gonadotrophin), and gn-RH (gonadotrophin-releasing hormone) effective in terms of triggering ovulation were determined in a mouse ovulation test. Varying doses of the above preparations were subcutaneously injected, 48 hours after overstimulation by injection of 0.5 or 1.0 IU of PMSG. The animals were sacrificed for examination, after another 18-20 hours had passed. Roughly 50 per cent of all animals treated (threshold) in one and the same dosage group (n = 5) had ovulated in response to 0.02-0.1 IU of FSH per animal. The following FSH and PMSG dosages are recommended: 0.02, 0.04, 0.06, 0.08, and 0.1 IU of FSH, 0.6, 1.0, 1.4, 1.8, 2.2, 2.6, 3.0 IU of PMSG. When mouse ovulation tests were used in orientation studies, ovulation was regularly induced by Gn-RH doses per animal between 0.01 and 1.0 micrograms. Dosage spacings or increments should be specified with higher accuracy by further studies.     

Effect of Follicle Size and Follicle-Stimulating Hormone on Ovulation Induction and Embryo Recovery in the Mare

The timing of ovulation is an important component to many equine breeding strategies. The action of luteinizing hormone on ovulation induction has been recognized; however, potential effects of follicle-stimulating hormone (FSH) have been less defined. Objectives of this study were to determine whether (1) mares could be induced to ovulate follicles ≤30 mm; (2) equine FSH (eFSH) has a positive effect on ovulation induction, and (3) ovulation of small follicles would affect embryo recovery. Light-horse mares (n = 12) between 4 and 10 years of age were assigned to treatments when they had a dominant growing follicle with a mean diameter of 24, 28, or 35 ± 2 mm and endometrial edema. Treatments were (1) H35, human chorionic gonadotropin (hCG) at 35 ± 2 mm; (2) F35, eFSH at 35 ± 2 mm; (3) H28, hCG at 28 ± 2 mm; (4) FH28, eFSH and hCG at 28 ± 2 mm; (5) D28, deslorelin (gonadotropin-releasing hormone [GnRH] analog) at 28 ± 2 mm; (6) FH24/H24, hCG or eFSH and hCG at 24 ± 2 mm. Mares’ reproductive tracts were scanned at 24 ± 2-hour intervals after treatment to detect ovulation. Mares were inseminated, and embryos were collected. Numbers of mares that ovulated within 48 ± 2 hours after treatment were: H35, 8/8 (100%); F35, 8/14 (57%); H28, 7/12 (58%); FH28, 9/12 (75%); D28, 3/7 (43%) and FH/H24, 4/14 (29%). The number of mares that ovulated in 48 ± 2 hours for H35 was not different from that for FH28 but was higher (P < .05) than all other groups. Embryo recovery rates, diameters, developmental stages, and morphology scores were not different for mares ovulating 48 hours or less versus more than 48 hours after treatment or among treatment groups. Results of this study demonstrate that follicles ≤30 mm can be induced to ovulate with no effect on embryo recovery or quality, as assessed by stereomicroscopy.     

The efficacy of a single chain recombinant equine luteinizing hormone (reLH) in mares: induction of ovulation, hormone profiles, and inter-ovulatory intervals

The objectives of this study were to determine the efficacy of recombinant equine luteinizing hormone (reLH) in shortening the time to ovulation in cycling mares and to determine the effects of treatment on endogenous hormones and inter-ovulatory intervals. In study 1, mares of light horse breeds (3–20 years) were treated with either a vehicle, various doses of reLH, or human chorionic gonadotropin (hCG). Cycling mares were examined by palpation and ultrasound per rectum daily or every 12 h from the time of treatment to ovulation. In studies 2 and 3, jugular blood samples were collected daily or every 12 h from the time of treatment to ovulation for analysis of LH, follicle stimulating hormone (FSH), estradiol-17β (E₂), and progesterone (P₄) by radioimmunoassays (RIA). Increasing doses of reLH (0.3, 0.6, 0.75, and 0.9 mg) showed increasing effectiveness at inducing ovulation within 48 h of treatment. Treatments with the 0.75 and 0.9 mg doses of reLH resulted in 90% and 80% ovulation rates, which were similar to hCG treatment (85.7%). Except for the early rise in LH after treatment with 0.5, 0.65, and 1.0 mg of reLH, hormone profiles appeared to be similar between control and treated cycles. Inter-ovulatory intervals were similar between control and treatment cycles. In conclusion, reLH is a reliable and effective ovulatory agent that does not significantly alter endogenous hormone profiles or affect inter-ovulatory intervals.     

Attempts at Superovulation of Mares With Porcine Follicle Stimulating Hormone and Recombinant Equine Follicle Stimulating Hormone

Attempts to superovulate mares have been disappointing and expensive. Conflicting data exist on the effectiveness of porcine follicle stimulating hormone (pFSH) as a superovulatory treatment for horses. Recently, a recombinant equine FSH (reFSH) has become available with covalently linked alpha and beta subunits, which results in a longer half-life than endogenous FSH. The purpose of this study was to compare doses of pFSH and reFSH for superovulating mares. Twenty-nine mares received injections of 25, 50, 100, or 150 mg pFSH or 0.5 mg reFSH 2 times per day. Mares were used up to three times, with their second reproductive cycle serving as an untreated control. All treated mares were administered cloprostenol on the second day of treatment and given 2,500 IU of human chorionic gonadotropin 24 to 38 hours after the majority of large follicles were >30 mm. Mares with untreated control cycles also received cloprostenol, but deslorelin was used to induce ovulation. No response from superstimulation treatments differed (P > .1) from those of controls; mean ovulations per cycle ranged from 0.85 to 1.31; mean embryo recovery rates ranged from 0.66 to 1.08. Two of the eight mares treated with reFSH failed to ovulate. Porcine FSH was ineffective at inducing multiple ovulations at any dose. Although previous studies of reFSH yielded high ovulation rates, further research is needed to establish optimal protocols and to determine the cause of failed ovulations.     

Comparison of Compounded Deslorelin and hCG for Induction of Ovulation in Mares

Ovulation-inducing agents are routinely used in broodmare practice. The objective of this study was to compare the efficacy of two compounded deslorelin products and human chorionic gonadotropin (hCG) in inducing ovulation in a clinical reproduction program. Breeding records of 203 mares administered an ovulation-inducing agent during the 2006 breeding season were reviewed. Estrous cycles were included for comparison if agents were administered when the largest follicle was 35 to 45 mm in diameter and endometrial edema was present. There was no significant difference (P > .05) in interval to ovulation for mares receiving deslorelin (1.9 ± 0.7 days) or hCG (2.0 ± 0.7 days). The percentage of mares that ovulated within 48 hours after treatment was also not significantly different between the agents (90.1% and 88.3%, respectively). In summary, clinical efficacy at inducing a timed ovulation in estrual mares with follicles 35 to 45 mm was similar between compounded deslorelin and hCG.     

BMPR-IB基因在寒泊羊群体中的增羔效应、遗传规律及育种应用分析

旨在揭示BMPR-IB基因在寒泊羊种群中的多态性及遗传学规律,探讨将BMPR-IB基因第746位碱基发生的A→G突变（FecB突变）作为分子标记进行绵羊多胎品种选育的科学性。本研究对寒泊羊育种核心群的健康种公羊、繁殖母羊、羔羊共计1 267只绵羊个体进行采血,利用PCR-RFLP方法判定个体BMPR-IB基因位点的基因型并进行群体遗传学分析。对繁殖母羊共计980胎次的产羔记录进行统计,分析FecB突变、胎次及产羔季节对胎产羔数性状的影响。统计所设计杂交组合后代共计167只健康羔羊的基因型比例。结果表明,BMPR-IB基因在寒泊羊种群中有BB、B+和++3种基因型,其基因型频率分别为1.97%、73.40%和24.63%,等位基因B和+的频率分别为38.67%、61.33%;BB、B+和++基因型繁殖母羊的平均胎产羔数分别为2.69、1.91、1.57只,目前寒泊羊种群的胎产羔数平均为1.85只;若经过品种选育使寒泊羊个体中增加一个B基因拷贝,胎产羔数预期增加0.44只;父母本杂交组合为B+×++的后代中B+和++基因型的比例为1.11：1,父母本杂交组合为B+×BB的后代中BB和B+基因型的比例为0.82：1,均符合孟德尔分离定律;预测经过6个世代的选育,可使寒泊羊种群母羊基本实现胎产羔数2只的育种目标。本研究结果为绵羊育种实践中制定选种和选配方案提供了理论基础。     

Effect of eFSH on Ovarian Cyclicity and Embryo Production of Mares in Spring Transitional Phase

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 F_2α (PGF_2α), on the day of embryo flushing. Three superovulated mares did not cycle immediately after PGF_2α 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.     

Superovulatory response and embryo quality in Katahdin ewes treated with FSH or FSH plus eCG during non-breeding season

The aim of this study was to evaluate the effect of a co-treatment of follicle-stimulating hormone (FSH) plus equine chorionic gonadotrophin (eCG) on serum insulin and insulin-like growth factor 1 (IGF-1) concentrations, superovulatory response, ovulatory rate, and number and production of embryos in Katahdin breed ewes during the non-breeding season. Twenty Katahdin ewes were synchronized with progestagens (CIDR) and assigned to two superovulation treatments (n = 10): (1): ewes treated with 200 mg ewe⁻¹ of FSH from day 5 to 8 after CIDR insertion at decreasing doses every 12 h (FSH group) and (2) ewes treated as FSH group plus 300 IU of eCG on day 5 after CIDR insertion (FSH + eCG group). Estrous behavior was monitored and direct mating was performed. On days − 7 (CIDR insertion), 0 (CIDR withdrawal), and 7 (embryo recovery), blood samples were collected to determine serum hormone concentrations. Co-treatment with eCG (FSH group) did not affect (P > 0.05) serum hormone levels. Superovulation response, ovulation rate, recovery rate, fertilization, and number of embryos were also similar (P > 0.05) between treatments. Compared with FSH group, FSH + eCG ewes had lower (P < 0.05) number of transferable embryos and higher (P < 0.05) number of oocyte and a tendency to increase the number of degenerated embryos (P = 0.07). Overall results suggest that the administration of eCG is not beneficial either to improve the ovulatory response or the amount of transferable embryos in Katahdin ewes superovulated with a protocol using progesterone and FSH at decreasing doses.

     

Timing of induction of ovulation in mares treated with Ovuplant or Chorulon

Reliable induction of timed ovulation is an important managerial tool in any horse-breeding operation. Not only does breeding close to ovulation increase pregnancy rates when using cooled, frozen, or poor-quality semen, but it also reduces the number of inseminations needed per cycle, resulting in a more efficient breeding program. To better predict ovulation time in the long estrus period of the mare, one could increase the frequency of transrectal palpations and ultrasounds and/or implement hormonal therapies to induce ovulations. However, previous studies have been unclear on the exact timing of ovulation of mares treated with human chorionic gonadotropin (Chorulon, Intervet Inc, Millsboro, DE) or deslorelin acetate (Ovuplant, Pharmacia and UpJohn Co, Kalamazoo, MI). This study was designed to determine the timing of ovulation after Ovuplant or Chorulon treatment in normal cycling mares presented to the veterinary clinic. In addition, the pregnancy rates were determined for mares bred when a single insemination, using frozen or chilled semen, was performed at a fixed time (36 hours) after Ovuplant or Chorulon treatment. Thirty-two mares were given a subcutaneous injection of 7.5 mg of prostaglandin F2α (Lutlyse, Ft Dodge Animal Health, Ft Dodge, IA) 5 days after the last ovulation and were examined every 48 hours until estrus was detected based on a dominant follicle and the presence of endometrial edema as determined by ultrasonographic examination. Group 1 (N = 12) was treated intravenously with 2,500 units of Chorulon, and group 2 (N = 20) was treated subcutaneously with Ovuplant as soon as mares were determined to be in estrus. Once treated all mares were examined by rectal palpation and ultrasound at 0, 12, 24, 28, 30, 32, 34, 36, 38, 40, 42, 44, 48, 60, 72, 84, 96, hours or until ovulation was detected. Ovulation rate in response to Chorulon was 83.3% at 48 hours, 91.6% at 72 hours, and 100% at 96 hours. All of the mares in the Ovuplant-treated group had ovulated by 48 hours. Chi-square analysis of the data showed a significant (P < .01) variation in the distribution of ovulation times between mares treated with Chorulon and mares treated with Ovuplant. This study provides enough evidence to support the hypothesis that timing of ovulation is a more reliable event in mares treated with Ovuplant compared with those treated with Chorulon.     

Efficacy of the gnrh agonist deslorelin acetate for inducing ovulation in mares relative to age of mare and season

Deslorelin acetate (Ovuplant™, Fort Dodge), a GnRH agonist, is commonly used to induce ovulation in cycling mares. Although its efficacy in hastening ovulation has been previously reported, the effects of age of mare and month of administration on percent of mares responding and interval to ovulation have not been studied.Data was gathered from reproduction records of 376 mares receiving deslorelin acetate at the Equine Reproduction Laboratory, Colorado State University, from 1995 to 1999. Age of mare, date of administration, size of largest follicle at treatment, and interval to ovulation were recorded. Age of mare was categorized into five groups: 2–4, 5–9, 10–14, 15–19, and greater than or equal to 20 years. Date of administration was divided into four groups: March and April, May and June, July and August, and September and October.A higher (p < 0.05) percentage of mares aged 10–14 (98.5%) ovulated in response to deslorelin acetate than mares aged 2–4 or 5–9 (90.2% or 91.0%, respectively) or mares aged 15–19 or ≥ 20 (87.9% or 83.8%, respectively). Mares ≥ 20 had the lowest ovulation rate (83.8%). However, mares ≥ 20 that responded to deslorelin acetate had a shorter (p < 0.05) interval from treatment to ovulation (1.7 ± 0.1 days) than mares 2–4 and 5–9 years of age (1.9 ± 0.1 and 1.9 ± 0.0 days, respectively).Deslorelin acetate was more effective in inducing ovulation in the July and August (95.4%) (p < 0.01) and September and October (95.7%) (p = 0. 04) than in the March and April (81.1%). Mares treated in May through October also experienced shorter (p < 0.05) intervals to ovulation than mares treated in March and April.     

Effect of deslorelin acetate on gonadotropin secretion and ovarian follicle development in cycling mares

OBJECTIVE: To evaluate gonadotropin secretion and ovarian function after administration of deslorelin acetate to induce ovulation in mares. DESIGN: Randomized controlled trial. ANIMALS: 16 healthy mares with normal estrous cycles. PROCEDURE: 8 control mares were allowed to ovulate spontaneously, whereas 8 study mares received deslorelin to induce ovulation when an ovarian follicle > 35 mm in diameter was detected. Follicle development and serum concentrations of gonadotropins were monitored daily during 1 estrous cycle. Pituitary responsiveness to administration of gonadotropin-releasing hormone (GnRH) was evaluated 10 days after initial ovulation. RESULTS: Interovulatory intervals of mares treated with deslorelin (mean +/- SD, 25.6 +/- 2.6 days) were longer than those of control mares (22.9 +/- 1.8 days). Diameter of the largest follicle was significantly smaller during 2 days of the diestrous period after ovulation in deslorelin-treated mares than in control mares. Concentrations of follicle-stimulating hormone (FSH) were lower in deslorelin-treated mares on days 5 through 14 than in control mares. Concentrations of luteinizing hormone were not different between groups during most of the cycle. Gonadotropin release in response to administration of GnRH was lower in mares treated with deslorelin acetate than in control mares. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of deslorelin was associated with reduction in circulating concentrations of FSH and gonadotropin response to administration of GnRH during the estrous cycle. Low concentration of FSH in treated mares may lead to delayed follicular development and an increased interovulatory interval.     

BMPR-IB基因对绵羊外周血生殖激素水平的影响

为研究不同BMPR-IB基因型多胎萨福克羊外周血中生殖激素水平的差异,以培育的发情期多胎萨福克母羊为实验对象,应用PCR-RFLP技术检测个体的BMPR-IB基因型,ELISA方法检测绵羊外周血中E2、FSH、LH、PRL和P4的含量,分析BMPR-IB基因型与5种生殖激素水平的相关性.结果表明：多胎萨福克羊群体中存在BMPR-IB基因的BB、B＋和＋＋三种基因型.＋＋基因型个体的平均E2含量和P4含量显著低于B＋基因型和BB基因型个体（P＜0.05）,3种基因型个体间平均FSH含量、LH含量和PRL含量差异均不显著（P＞0.05）.BMPR-IB基因突变导致发情期母羊的雌二醇和孕酮的分泌量增加.研究结果可为合理利用BMPR-IB基因培育多胎肉羊提供依据.     

Ovulation,Pregnancy Rate and Early Embryonic Development in Vernal Transitional Mares Treated with Equine‐ or Porcine‐FSH

The objective of this study was to compare the efficacy of purified equine‐ and porcine‐FSH treatment regimes in mares in early vernal transition. Mares (n = 22) kept under ambient light were examined ultrasonographically per‐rectum, starting January 30th. They were assigned to one of two treatment groups using a sequential alternating treatment design when a follicle ≥ 25 mm was detected. In the eFSH group, mares were treated twice daily with equine‐FSH, and in the pFSH group mares were treated twice daily with porcine‐FSH; treatments were continued until follicle(s) ≥ 35 mm, and 24 h later hCG was administered. Oestrous mares were inseminated with fresh semen and examined for pregnancy on days 11–20 post‐ovulation. In the eFSH group, 11/11 (100%) mares developed follicle(s) ≥ 35 mm, 8/11 (73%) ovulated and 6/8 (75%) conceived. In the pFSH group, 5/11 (45%) developed follicle(s) ≥ 35 mm, 4/11 (36%) ovulated and 3/4 (75%) conceived. Treatment with eFSH resulted in a greater ovarian stimulation; higher number of pre‐ovulatory‐sized follicles, higher number of ovulations and higher number of embryos (p < 0.05). Following ovulation, serum progesterone concentrations were correlated with the number of CLs and supported early embryonic development; maternal recognition of pregnancy occurred in all pregnant mares. We concluded that eFSH can be used to effectively induce follicular growth and ovulation in vernal transitional mares; however, if bred, diagnosis and management of twins’ pregnancies would be required prior to day 16 because of the increased risk of multiple embryos per pregnancy. Conversely, the current pFSH treatment regime cannot be recommended.