Short-term changes in serum luteinizing hormone, ovarian response and reproductive performance following gonadotrophin releasing hormone treatment in postpartum dairy cows with retained placenta.

Thirty-six postpartum Holstein cows consisting of eighteen cows that shed the placenta soon after calving (NRP) and eighteen cows that retained placenta greater than 24 h (RP) were used. There were four treatment groups. Group I consisted of 9 NRP cows which received intramuscular injection of sterile saline on day 15 postpartum. The second group consisted of 9 NRPN cows which received 100 micrograms of gonadotrophin releasing hormone on day 15 postpartum (NRPT). The third group consisted of 9 RP cows which received saline on day 15 postpartum (RPN) and the fourth group consisted of 9 RP cows which received 100 micrograms of gonadotrophin releasing hormone on day 15 postpartum (RPT). Blood samples were collected once daily during the first month and once every other day during the second month postpartum. In addition fourteen cows (RPT, n = 7; NRPT, n = 7), were used to study short-term changes in serum luteinizing hormone concentrations following gonadotrophin releasing hormone treatment on day 15 postpartum. Blood samples were obtained from these cows every 15 min during 1 h before and 6 h after gonadotrophin releasing hormone administration. Sera from all samples were assayed for progesterone and luteinizing hormone concentrations. Starting from four days after calving rectal palpations and ultrasound examinations of the ovaries were carried out once every four days until day 28 postpartum in order to monitor ovarian changes. All cows were inseminated on the first estrus after day 60 postpartum and examined for pregnancy between 35 and 42 days after insemination.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of gonadotrophin releasing hormone administration four days after insemination on first-service conception rates and corpus luteum function in dairy cows.

One hundred and eighty-five Holstein-Friesian dairy cows received either sterile water or 250 micrograms of gonadotrophin releasing hormone intramuscularly on the fourth day after the first service postpartum. Heparinized blood samples were taken immediately prior to treatment (day 4) and on day 8 postinsemination for analysis of plasma progesterone concentration. Pregnancy diagnosis was carried out by rectal palpation at 42 days postinsemination and reconfirmed after 60 days postbreeding. The pregnancy rates after first, second or third service were not significantly different between gonadotrophin releasing hormone-treated and control cows. Plasma progesterone concentrations on day 4 and day 8 postinsemination, as well as the change in plasma progesterone concentration from day 4 to day 8, were similar for gonadotrophin releasing hormone-treated and control cows. The plasma progesterone concentrations on day 8 postbreeding were significantly higher (p less than 0.005) and the change in progesterone concentrations between days 4 and 8 were significantly greater (p less than 0.002) in pregnant cows compared to nonpregnant cows.     

Interrelationships between postpartum events, hormonal therapy, reproductive abnormalities and reproductive performance in dairy cows: a path analysis.

Path analysis was used to determine the interrelationships between postpartum administration of gonadotrophin releasing hormone and cloprostenol and the occurrence of reproductive disease and reproductive performance in dairy cows. The data analysed were those collected on 226 Holstein-Friesian cows calving in a commercial dairy herd during a 17 month period (May 1, 1981 to October 1, 1982). Cows administered gonadotrophin releasing hormone at day 15 postpartum experienced an improved rate of uterine involution as determined by rectal palpation nine days later. Although this improved rate of uterine involution reduced the risk of pyometritis, it actually directly delayed conception. Also, gonadotrophin releasing hormone therapy directly resulted in an increased incidence of pyometritis which in turn resulted in an increase incidence of cystic ovarian disease and anestrus. The occurrence of these abnormalities resulted in increased intervals from calving to first observed estrus, first service and conception. In addition to this effect, the administration of gonadotrophin releasing hormone was also associated with increased plasma progesterone concentrations at days 24 and 28 postpartum which delayed conception. Cloprostenol therapy at day 24 postpartum resulted in a decreased plasma progesterone concentration at day 28 postpartum which was directly and indirectly associated with a decrease in the calving to conception interval. The indirect effects were mediated by a reduction in days to first estrus. Cloprostenol therapy also directly resulted in a decreased calving to first observed estrus interval for reasons not attributable to the level of progesterone at day 28.     

Effects of Gn-RH on blood serum hormone concentrations, ovulation rates and embryo production in lactating cows treated with PMSG.

The effects of gonadotrophin releasing hormone injection into pregnant mare serum gonadotrophin treated cows on serum levels of luteinizing hormone, estradiol-17 beta and progesterone and ovulation rates was evaluated in 20 cows. Pregnant mare serum gonadotrophin treatment does not always induce superovulation as was shown in this study. Luteinizing hormone levels reached peak concentrations at 1.0 h and remained significantly (P less than or equal to 0.05) elevated at 2.0 h, 3.0 h, 4.0 h, and 7.0 h after the first gonadotrophin releasing hormone injection. Progesterone levels in the gonadotrophin releasing hormone treated group were significantly (P less than or equal to 0.05) higher than in the controls on the third and fourth days following injection. A significant correlation (r = 0.58-0.72) was noted between the number of corpus luteum and progesterone levels on each day between day 2 and day 7. More embryos were recovered (46 vs 26) from the ten treated than from the ten control cows.     

Bovine cystic ovarian disease: plasma hormone concentrations and treatment.

Ovarian function in 91 dairy cows with cystic ovarian disease was assessed by rectal palpation and by plasma hormone analysis before and after treatment. Plasma analysis showed that 84% of the cysts were correctly classified clinically and only these cows are considered further. Luteinised cysts occurred in 59 cows whereas only 18 had non-luteinised cysts. The mean plasma concentrations of luteinising hormone (LH), follicular stimulating hormone (FSH), progesterone, oestradiol and testosterone were not significantly different when compared with values at relevant stages of the oestrous cycle in normal cows. Success of treatment with progesterone, a synthetic prostaglandin, human gonadotrophin (HCG), or gonadotrophin releasing hormone (GnRH) was not dependent upon prior hormone concentrations, except for the prostaglandin which required active luteal tissue. LH and FSH concentrations in cows with luteinised cysts were not significantly different before and after successful treatment with GnRH or progesterone. Normal luteal function was not always established after treatment of non-luteinised cysts with GnRH.     

Recent Developments in Oestrous Synchronization of Postpartum Dairy Cows with and without Ovarian Disorders

This report reviews the most recent developments in prostaglandin‐based oestrous synchronization programmes for postpartum dairy cows and addresses the efficiency of controlled breeding protocols based on such developments for cows with abnormal ovarian conditions. A double prostaglandin protocol applied 11–14 days apart seems to be capable of bringing most cows to oestrus. Because of varying oestrus onset times, improved conception rates are obtained following artificial insemination (AI) at detected oestrus rather than fixed‐time AI in prostaglandin‐treated cows. The administration of oestradiol or human chorionic gonadotrophin, or both these hormones, after prostaglandin treatment, improves the synchrony of oestrus yet does not enhance the conception rate. Progesterone‐based treatments for oestrous synchronization are considered the most appropriate for non‐cyclic or anoestrous postpartum dairy cows; prostaglandin alone being ineffective because of the absence of a mature corpus luteum in these cows. Improved oestrus synchrony and fertility rate have been reported using short‐term progesterone treatment regimes (7–9 days) with or without oestradiol benzoate combined with the use of a luteolytic agent given 1 day before, or at the time of, progesterone withdrawal. The ovulation synchronization (Ovsynch) protocol, based on the use of gonadotrophin releasing hormone and prostaglandin, was developed to coordinate follicular recruitment, CL regression and the time of ovulation. This protocol allows fixed time insemination and has proved effective in improving reproductive management in postpartum dairy cows. However, timed AI following Ovsynch seems to have no beneficial effects in heifers, because of an inconsistent follicle wave pattern, and in anoestrous cows, given their lack of prostaglandin responsive CL. To date, there are several prostaglandin based, fixed‐time insemination oestrous synchronization protocols for use in early postpartum dairy cows with ovarian disorders such as ovarian cysts and acyclicity.     

Chronic cystic ovarian disease in a Holstein cow

Cystic ovarian follicles are commonly found during rectal examination of early postpartum dairy cows, usually presenting with anoestrus and occasionally nymphomania. Most cases self cure with time, or respond to exogenous hormonal treatment. This case report describes a refractory case in a Holstein cow in which a novel treatment approach was used. A gonadotrophin releasing hormone agonist implant was inserted for 180 d in an attempt to suppress pituitary gonadotrophin output, arrest abnormal ovarian follicle growth and prevent steroidogenesis. Frequent serial blood samples were collected before and after implant insertion to monitor changes in pulse release of luteinising hormone. Follow up ultrasound scans and blood samples were done to monitor ovarian structures; progesterone and oestradiol were collected at various times over the 180 d period. A normal, cycling herdmate was enrolled as a control. Prior to implant insertion, high frequency and low amplitude luteinising hormone pulses were detected in the cystic cow. Insertion was followed by a sustained surge in the release of luteinising hormone in both cows, but ovulation was not induced in the cystic cow. Plasma oestradiol levels remained consistently elevated and signs of oestrous behaviour were observed. Long term gonadotrophin releasing hormone agonist treatment failed to suppress either ovarian steroid production or cause regression of the cysts by 180 d.     

Reproductive performance in dairy cows following postpartum treatment with gonadotrophin releasing hormone and/or prostaglandin: a field trial.

Three hundred and five Holstein Friesian cows were given either 250 micrograms gonadotrophin releasing hormone (GnRH) or saline on day 15 postpartum followed by 500 micrograms cloprostenol or saline on day 24 postpartum. Four treatment groups were formed using random allocation: Group I -- placebo (Day 15)/placebo (Day 24), Group II -- GnRH (Day 15)/placebo (Day 24), Group III -- placebo (Day 15)/cloprostenol (Day 24), Group IV -- GnRH (Day 15)/cloprostenol (Day 24). Double blind techniques were used during the follow-up period. Rectal palpation, to assess uterine involution and ovarian activity was performed just prior to each treatment and again at 28 days postpartum. In addition blood samples were collected at 15, 24 and 28 days postpartum for measurement of plasma progesterone. There were no significant differences among treatment groups with respect to services per conception, number of heats detected before first service and culling for infertility. Cows treated only with GnRH had an increased calving to first estrus and calving to first breeding interval, and tended to have an increased calving to conception interval. Treatment with cloprostenol significantly decreased calving to conception and calving to first observed estrus intervals. Treatment with GnRH on day 15 postpartum resulted in a significant increase in the subsequent incidence of pyometra and prebreeding anestrus. On the other hand, cloprostenol treatment on day 24 postpartum resulted in a decreased incidence of pyometra, regardless of GnRH treatment and a decreased incidence of prebreeding anestrus in GnRH treated cows compared to cows receiving only GnRH at day 15 postpartum.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of gonadotrophin releasing hormone on reproductive performance of dairy cows with retained placenta.

The effects of gonadotrophin releasing hormone (GnRH) on the reproductive performance of dairy cows with retained placenta were studied. Three hundred and seventy-eight cows diagnosed as having retained placenta received intramuscular injections of either 2 mL sterile water or 200 micrograms of GnRH in 2 mL sterile water between day 8 and day 14 postpartum. Rectal palpation was performed at the time of treatment and ten to 20 days after treatment in order to determine the rate of uterine involution. Thereafter, monthly rectal examinations were carried out until insemination. Pregnancy diagnosis was made by rectal palpation at 40 days or more after breeding. Using the entire experimental population, there were no significant differences between GnRH-treated and control cows for the rate of uterine involution, the occurrence of reproductive problems, the interval from parturition to first observed estrus, the interval from parturition to first insemination, the interval from parturition to conception, the number of services per conception, the total number of services per cow regardless of conception and the incidence of culling for infertility. When the data for herds in which breeding began earlier in the postpartum period (herds having a mean less than or equal to 80 days from parturition to first service for retained placenta cows) were considered, the GnRH treatment resulted in a significantly shorter (p less than or equal to 0.01) calving to conception interval as compared to control cows. Also, there was a significant reduction (p less than or equal to 0.05) in the total number of services per cow regardless of conception and a significant reduction in the interval from parturition to first service.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interrelationships between ambient temperature, age at calving, postpartum reproductive events and reproductive performance in dairy cows: a path analysis.

Path analysis was used to determine the interrelationships between ambient temperature, age at calving, postpartum reproductive events and reproductive performance in dairy cows. The data used in the analysis were collected on 226 Holstein-Friesian cows calving in a commercial dairy herd during a 17 month period (May 1, 1981 to October 1, 1982). The data were obtained from a double blind study evaluating the effects of gonadotrophin releasing hormone and cloprostenol in postpartum cows. Rectal palpation to assess uterine involution and ovarian activity was performed on each cow on days 15, 24 and 28 postpartum. At the same time, blood samples were collected for subsequent progesterone assay. Data were recorded on the occurrence of reproductive diseases and events from the time of parturition until the diagnosis of pregnancy or until the cow left the herd in the case of culled cows. There was an increase in the incidence of retained placenta, in the percentage of cows with abnormal vaginal discharge in the early postpartum period as well as a delay in uterine involution during the winter months. In addition, cows calving during the winter had prolonged intervals to first estrus, first service and conception compared to cows calving during the summer. (Cows calving during the warmest months, on average, were seen in estrus 24 days sooner, received first service 42 days sooner and conceived 27 days sooner than cows calving during the coldest months of the year).(ABSTRACT TRUNCATED AT 250 WORDS)     

黄牛孪生处理前后发情周期的外周血中GnRH水平

在母牛产后第1次发情后第10d，给5头发情周期正常的母牛安装颈静脉血管导管；在母牛产后第2个发情周期进行挛生处理，即在产后第2次发情后第10d注射PMSG2000IU，2d后注射氯前列烯醇0．4mg第3次发情后注射抗PMSG抗体2000IU。自第1个发情周期第10d开始，每天间隔10min连续采血2h。发情当天间隔30min采血一次，直到第3次发情结束为止。挛生处理后采血间隔时间和方法与处理前不同。应用酶免疫测定方法测定血清中促性腺激素释放激素水平。结果表明：（1）牛外周血中GnRH释放具有脉冲性；（2)PMSG处理后外周血中GnRH水平升高，表现为脉冲频率增加，脉冲峰值升高。     

Hypoglycemia alters pulsatile luteinizing hormone secretion in the postpartum beef cow

This study tested the hypothesis that the increased glucose requirement of lactation had effects that were independent of the suckling-dependent inhibition of postpartum endocrine function in beef cows. Mature Hereford cows were either suckled ad libitum and infused with saline iv (n = 9) from d 2 through 4 (d 0 = jugular catherization on d 32 +/- 3 postpartum); were nonsuckled and infused with saline from d 2 through 4 (n = 10); or were nonsuckled and infused with phlorizin (3 g/d) from d 2 through 4 (n = 10). Nonsuckled cows infused with phlorizin had lower (P less than .05) plasma concentrations of glucose and amino acid nitrogen (AAN) on d 2 compared with pre-infusion levels (d 1), but their metabolic profile returned to levels similar to the suckled cows by d 3 and 4. Nonsuckled cows infused with saline had elevated glucose and insulin and lower AAN and free fatty acids (FFA) on d 3 and 4 compared with pre-weaning (d 1) levels (P less than .05). Nonsuckled cows infused with phlorizin did not show this weaning-induced elevation in glucose and insulin. The number of luteinizing hormone (LH) pulses was not affected by treatment. However, in contrast to the large LH pulses observed in the nonsuckled cows infused with saline, both the suckled cows and the nonsuckled cows treated with phlorizin had more small and fewer large amplitude pulses (P less than .01). Treatment did not affect serum concentrations of follicle stimulating hormone, gonadotropin release in response to gonadotropin releasing hormone (25 micrograms) or the number of cows ovulating by 55 d after calving. We conclude that the increased glucose clearance caused by phlorizin infusion or lactation results in depression of LH pulse amplitude in suckled postpartum beef cows.     

Clearance rate of gonadotrophin releasing hormone in peripheral plasma of the pig.

Gonadotrophin releasing hormone was administered as an intravenous bolus injection into four boars and four ovariectomized sows. Radioimmunoassay of concentrations of gonadotrophin releasing hormone in blood collected periodically after injection indicated a biexponential decline suggesting a rapid distribution to the extracellular fluid and a slower elimination by metabolism. A mean half-life value of 2.12 +/- 0.95 (SD) minutes was calculated for the first component and of 13.15 +/- 2.55 minutes was calculated for the second component of the decline in gonadotrophin releasing hormone concentrations. No significant difference was detected between boars and sows for half-life value of either component. In the four boars, luteinizing hormone values reached a peak in plasma 20 minutes after injection and that of testosterone at 90 minutes after gonadotrophin releasing hormone treatment.     

Hormonal treatments for fertility disorders in cattle

In dairy cows, hormonal treatments are commonly implemented for acyclicity, silent heat and endometritis. Before treatment, causes of infertility need to be detected and severe failures in housing, feeding or other diseases must be eliminated. Without sustainable improvement of herd management, the use of intensive hormonal treatments will not improve reproductive performance. The most common cause of anoestrous is silent heat. In cows with a palpable corpus luteum, injection of prostaglandin F2α (PGF) reliably induces oestrous. A satisfactory treatment for acyclicity (ovarian dystrophy, ovarian cysts) does not exist. Combinations of different hormones have greater treatment success than a single use of gonadotrophin releasing hormone (GnRH) or human chorionic gonadotrophin (hCG). Strategic use of PGF during the early postpartum period cannot be recommended because positive effects on uterus involution and resumption of the oestrous cycle after calving have not been verified. In contrast, application of GnRH combined with PGF in the puerperal phase appeared to have positive effects on fertility of cows with endometritis. The same applies to PGF for cows with chronic endometritis. Cases of endometritis with fetid odour of vaginal mucus or isolation of Trueperella pyogenes should be treated with antibiotics. Treatment before the 27th day post partum is not advisable. In conclusion, hormonal treatments can be used to treat fertility disorders. Nevertheless, in order to enhance the reproductive performance at the herd level, a sustainable improvement of the general conditions (housing, feeding, animal health, management) is a prerequisite.     

Luteinizing hormone concentrations in serum of postpartum beef cows injected with microencapsulated luteinizing hormone-releasing hormone analog

Twenty-five cows were divided equally into five groups to determine whether [D-Trp6]-luteinizing hormone releasing hormone (LHRH-A) microencapsulated in poly (DL-lactide co-glycolide) would increase basal serum concentrations of LH during the postpartum period. On d 5 postpartum, cows were injected i.m. with 2 ml of vehicle alone (Group 1) or vehicle containing microcapsules calculated to release .4, 1.6, 6.4 or 25.6 micrograms LHRH-A per day for approximately 30 d (Groups 2, 3, 4 and 5, respectively). Cows were bled every 15 min for 4 h immediately before and after injection and every 15 min for 4 h at weekly intervals for the next 4 wk to evaluate serum profiles of LH. Estrus was determined by twice daily observations and confirmed by serum progesterone. More cows in Groups 2, 3, 4 and 5 exhibited pulsatile patterns of LH after LHRH-A injection than in Group 1 (P less than .06). More pulses of LH were observed after LHRH-A injection in Groups 4 and 5 than in Group 1 (P less than .01). Mean concentrations of LH within treatment groups did not change during the initial injection, except in Group 5. All cows in Group 5 had a surge of LH immediately after injection. The induced surge of LH in two cows in Group 5 cows resulted in progesterone profiles similar to those during a normal luteal phase. Days to first postpartum estrus were not different among the five treatment groups. Microencapsulated LHRH-A given at a dose estimated to release 25 micrograms LHRH-A/d was effective in elevating LH concentrations following injection. However, effectiveness of this hormonal treatment in shortening postpartum anestrus was not substantiated.     

Relationship between weaning and secretion of luteinizing hormone, cortisol and transcortin in beef cows

The effects of suckling on secretion of luteinizing hormone, cortisol and transcortin were investigated in anovulatory postpartum cows. On d 35 postpartum, calves were separated from 12 cows to prevent suckling and eight calves continued to suckle their dams ad libitum. Between 35 and 41 d postpartum, samples of jugular blood were collected every 15 min for two periods of 6 h/d. In non-suckled cows, frequency of pulses and basal luteinizing hormone increased but amplitude of pulses did not change. Concentrations of total cortisol in serum of cows were not altered during 3 d after weaning calves and did not differ among intervals before, during and after a suckling event. Affinity of transcortin for cortisol was not affected by postpartum interval or treatment. Capacity of transcortin to bind cortisol tended to increase after weaning. We found no evidence to support the hypothesis that suckling reduces binding capacity of transcortin or increases unbound cortisol. Differences in preovulatory secretion of luteinizing hormone between suckled and non-suckled cows could not be accounted for by differences in secretion of cortisol. In beef cows that are fed to satisfy requirements for energy and have average body condition, we conclude that negative modulation of luteinizing hormone by suckling is not mediated by cortisol.     

产后无发情和亚发情母牦牛激素诱导发情试验

选择怀孕母牦牛84头,在生产前后1个月进行补饲,其中40头在产后当年发情季节进行激素诱导发情试验,44头作对照;另选择60头自然生产的产后母牦牛在发情季节进行单纯的激素诱导发情试验,60头作对照.激素诱导发情方法是0 d注射氯前列烯醇0.2 mg,7 d后注射促黄体素释放激素A3 25 μg,连续3 d;在0和7 d进行直肠检查和血样采取,血样进行孕酮测定;测定处理时母牦牛卵巢状态,观察母牦牛发情配种受孕情况.结果显示,通过直肠检查和血浆孕酮测定,发现无发情状态的产后母牦牛占产后牦牛的63.33%和65%,亚发情的产后母牦牛占产后牦牛的36.67%和35%.采用氯前列烯醇和促性腺激素释放激素处理方案进行诱导发情,26.67%的产后母牦牛在处理后出现了发情;对怀孕母牦牛在围产期进行补饲,产后母牦牛在发情季节采用氯前列烯醇和促性腺激素释放激素诱导发情,有45.45%的产后母牦牛恢复了发情,而只补饲不进行激素诱导发情的母牦牛只有20%的母牦牛出现了发情;通过孕酮测定发现2组中激素诱导发情成功的母牦牛中,有68.18%和72%是处于亚发情状态的母牦牛.结果表明,氯前列烯醇和促性腺激素释放激素进行诱导发情的处理方案适合于产后亚发情状态的母牦牛.     

Efficacy of gonadotropin-releasing hormone administered at the time of artificial insemination of heifers and postpartum and repeat breeder dairy cows

The efficacy of gonadotropin releasing hormone (GnRH) on the fertility of dairy heifers and postpartum cows was studied. In one study, 300 cows were assigned randomly to 1 treatment from a 2 X 2 design, and 2 ml of 0.15M saline solution or 100 micrograms of GnRH was given IM on postpartum day (PPD) 14 and at the time of 1st postpartum breeding. In a 2nd study, repeat breeder cows (n = 346) were given saline solution or GnRH at the time of the 3rd breeding. In a 3rd study, heifers (n = 185) were given saline solution or GnRH at 1st breeding. Animals were observed for repeat estrus, and pregnancy diagnoses were made by rectal palpation 45 to 60 days after breeding. Conception rates were 15% to 18% higher for cows given GnRH, whether at PPD 14 or at the first postpartum breeding. When GnRH was given at the first breeding, conception rates were significantly higher (P less than 0.05). Conception rates for repeat breeder cows given GnRH were 25% higher than those in controls (P less than 0.005). Conception rates for heifers did not differ between treatments.     

Response to selection for milk yield and metabolic challenges in primiparous dairy cows

The effect of selection for milk yield on lactation yield, net energy balance, and on plasma growth hormone, insulin, prolactin, nonesterified fatty acids and glucose was studied in two groups of primiparous Holstein cows of differing genetic merit. Net energy balance was calculated and serial blood samples were collected for a 7 hr period at 0, 45, 90 and 180 days postpartum. Growth hormone releasing factor (.2 μg/kg BW) was administered after 2.5 hr at 0, 45 and 180 days postpartum, while epinephrine (.7 μg/kg BW) was administered at 90 days postpartum, Milk yield was greater, net energy balance was decreased and plasma growth hormone was greater in genetically superior selection group cows compared to control cows.

Growth hormone showed similar increases in both genetic groups in response to growth hormone releasing factor, while prolactin, insulin and glucose were not altered. Epinephrine stimulated an increase in plasma nonesterified fatty acid, glucose and insulin, but responses did not differ between genetic groups. Results indicate differences exist in production efficiency, net energy balance and plasma growth hormone concentration among dairy cattle as a result of selection for milk yield and suggest that selection pressure may act to alter homeorhetic control of nutrient metabolism.     

绵羊高繁殖力内分泌学机制的研究进展

作者从促性腺激素释放激素(G nRH)、促卵泡素(FSH)、促黄体素(LH)、抑制素(INH)、孕酮、雌二醇等方面综述了绵羊高繁殖力内分泌学机制的研究进展。