应用激素诱导家兔同期发情和提高受胎率的研究

<正> 家兔是诱发排卵的动物,发情母兔经交配刺激后,脑下垂体前叶释放促黄体生成素(LH),从而引起卵巢排卵。因此,在家兔人工受精前用激素促使母兔卵泡发育和排卵,就可以不经公兔爬跨而使母兔受胎。 我们应用国产孕马血清促性腺激素(PMSG)和促卵泡刺激素(FSH),作为促使卵泡发育和发情的药物;用绒毛膜促性腺激素(HCG)和促黄体生成素(LH),作为促使卵巢排卵的药物,诱导家兔同期发情和提高受胎率。     

生殖激素的生理功能

<正>1促黄体素促黄体素(LH)和促卵泡素(FSH)协同作用可促进卵巢血液加速,卵泡最后成熟并分泌雌激素。发情后期,在FSH作用的基础上LH突发性分泌引起成熟卵泡排卵,黄体形成。这种生理机能的出现,孕激素的作用是很重要的。LH通过卵泡壁细胞的环磷酸腺苷(cAMP)促进了孕激素的合成,孕激素则能刺激卵泡壁细胞的蛋白分解酶、胶原水解酶的合成,由于这种酶的出现,分解了卵泡壁细胞而引起排卵。因     

促黄体激素基因(LH)与产仔数性状关系的初步研究

促黄体激素基因(LH)是一种糖蛋白激素，与FSH一样是诱发排卵的主要因素之一。在雌性哺乳动物，LH的主要作用是与FSH协同促进卵泡生长成熟。参与内膜细胞合成雌激素，并可诱发排卵，促进黄体生成。另外还有增加血流量的作用。目前，关于LH的结构和生理功能研究已取得了一定的进展，但将其作为产仔数性状的遗传标记来进行研究的报道还不是很多。此次试验采用PCR-SSCP方法。以不同的猪种作为研究对象。研究LH基因与产仔性状的关系。     

绒山羊泌乳期诱导发情效果及相关生殖激素变化

旨在研究燕山绒山羊母羊泌乳期诱导发情的效果及对相关生殖激素变化的影响。选择经产、体质量约为45 kg的泌乳期母羊45只,随机分为A、B和C组,分别于产后25,35,45 d采用孕酮阴道硅胶栓(CIDR)+促卵泡素(FSH)的方法诱导发情,统计96 h内发情率,在埋栓的0,4,9,13 d及试验羊发情时采血检测FSH、促黄体素(LH)、催乳素(PRL)、雌激素(E_2)和孕酮(P_4)浓度。结果显示,A、B和C组的发情率分别为60%,53.33%和80%,发情多集中在24～72 h;埋栓前,即试验0 d时A、B和C组FSH、LH、PRL、E_2和P_4无差异。FSH和LH在撤栓时达到最低,撤栓后升高;14～15 d,所有发情羊FSH和LH均高于未发情羊,但只有A、B组FSH差异显著(P0.05)。14～15 d,PRL浓度最低(P0.05);试验期间,除9 d外,C组发情羊PRL显著低于未发情羊(P0.05),其余各组内发情羊与未发情羊PRL无差异。14～15 d,3组发情羊血清中E_2迅速升高而P_4降低,E_2浓度高于埋栓期(P0.05),试验期间,各组内发情羊与未发情羊E_2和P_4无差异;0～15 d,各组发情羊之间及未发情羊之间PRL、P_4无差异,各组发情羊间FSH及未发情羊间E_2均无差异;4 d,A组未发情羊FSH低于B组(P0.05),LH高于C组(P0.05);13 d,B组发情羊LH低于C组(P0.05),14～15 d,E_2高于C组(P0.05)。结果表明,母羊产后45 d诱导发情效果较好;外源P_4可大幅度降低PRL,发情时FSH、LH和E_2的分泌同步上升。     

波尔山羊和本地山羊超数排卵和胚胎移植试验初报

采用常规超排方法，使用促卵泡素(FSH)对波尔山羊进行超排处理，其结果如下：用300IU的FSH对波尔山羊逐日渐量递减注射，在第一次配种的同时注射人绒毛膜促性腺激素(HCG)，2只波尔山羊卵巢上卵泡数和黄体数分别为50个和32个，回收的卵子数为22个，排卵率为64％，回收率为68．7％，可用胚胎率为0。本地羊超排处理后，3只羊卵巢上卵泡数和黄体数分别为66个和24个，排卵率为36．3％，回收的数为16个，回收率为66．7％，可用胚胎率为0。一以上结果表明：以300IU的FSH结合HCG对波尔山羊进行超排处理是有效的。而以相同的FSH剂量结合HCG处理本地山羊时。超排效果不甚理想。     

鹅就巢期卵巢特征及其内分泌机制的研究进展

鹅的就巢行为显著影响其产蛋量,就巢行为主要受下丘脑-垂体-性腺轴(HPG)分泌的相关激素调控。相关激素主要包括促性腺激素释放激素(GnRH)、催乳素(PRL)、促卵泡激素(FSH)、促黄体素(LH)、雌二醇(E_2)和孕酮(P_4),共同调控鹅的就巢行为。在就巢期,机体内PRL分泌浓度升高,能够抑制GnRH和FSH的分泌,导致大卵泡合成P_4、E_2速率下降,从而垂体分泌LH浓度降低。本文对鹅就巢期激素水平及卵巢形态变化进行阐述,以期通过调控鹅就巢行为来提高产蛋量的相关研究提供理论支持。     

催产素与氯前列烯醇在母猪生产上的应用

1 母猪繁殖周期中激素变化促卵泡素(FSH)是垂体前叶分泌的1种激素,可促进卵巢中卵泡的发育.卵泡成熟时分泌的雌激素会刺激母猪表现出典型的静立发情行为. 促黄体素(LH)刺激卵巢排卵,也是由垂体前叶分泌的.卵泡破裂释放出卵子之后,破裂卵泡内的细胞继续发育,形成黄体. 母猪的正常发情周期是21天,垂体前叶会在发情周期的后期,大约18～20天时分泌FSH.LH是在发情周期的0～2天分泌的,刺激排卵.     

不同来源抑制素抗原对牛羊繁殖力影响研究

<正>抑制素是一种由性腺分泌的糖蛋白,由α、β两个亚基组成。研究表明,它具有选择性抑制促卵泡素(FSH)合成和分泌的作用。最初在研究抑制素生理作用时发现,用卵泡液提取物免疫动物后,可提高排卵率,增加产仔数。另一方面的研究发现,在多产Booroola美利奴母羊卵巢中缺少具生物活性的抑制素,这说明这种母羊体内FSH浓度较高,这显然是由于该种母羊卵巢内缺少抑制素的结果。于是,上述现     

用多种促卵泡素产品超排黑白花母牛效果比较

本试验用国内外的6种FSH产品分12组超排黑白花母牛297头次。各组依次为(1)动物所pFSH,(2)动物所oFSH,(3)AUSAoFSH,(4)AUSA加剂量oFSH,(5)AUSApFSH,(6)Sigma FSH,(7)日本FSH,(8)宁波500单位,(9)宁波360单位,(10)武汉500单位,(11)武汉360单位,(12)武汉500单位加LH。冲卵时记录卵巢上的黄体数、卵泡数、采集的总卵数和可用胚胎数。经统计分析,第8和12组在各组中排卵数最高(P<0.05,或P<0.01除第11组),oFSH排卵数最低。有效胚胎数列在前6位的是第9、11、1、7、4和5组,第1-7组有效胚胎的比率较高(P<0.05或P<0.01)。使用宁波和武汉产的FSH,360单位比500单位效果要好,配种时注射LH可提高排卵数和有效卵数。冲卵时卵巢上的卵泡数与黄体数、采卵数和有效胚胎数没有明显相关(r<±0.02,P>0.05),而黄体数与采卵数(r=0.83)和有效胚胎数(r=0.67)为强相关,采卵数与有效胚胎数也呈强相关(r=0.81),且皆为差异极显著(P<0.01)。由此得出结论:oFSH比PFSH用于牛超排生物活性低;FSH质量与有效胚胎数有关,用高纯度的FSH超排可以提高胚胎的可用率。     

FSH和LH对延边黄牛卵母细胞体外成熟及重组胚发育的影响

实验主要研究促卵泡素(FSH)、促黄体素(LH)对延边黄牛卵母细胞体外成熟及重组胚发育的影响,从而提高延边黄牛体细胞克隆的效率。采集屠宰后延边黄牛卵巢,用抽吸法回收卵母细胞,然后在不同种类、浓度激素条件下进行卵母细胞的体外成熟培养,最后将成熟的卵母细胞进行核移植及重组胚的体外培养。实验分别比较了在0、5、10、15、20μg/mL条件下,单独使用FSH与LH和在15μg/mL的FSH与10μg/mL的LH共同作用下对延边黄牛卵母细胞体外成熟率、卵裂率和囊胚发育率的影响。结果表明:将卵母细胞单独置于加有浓度为15μg/mL的FSH和10μg/mL的LH的成熟液中培养,其成熟率及后期发育率优于其他浓度组(P<0.05);而2种最优浓度同时添加共同作用时要好于单独使用(P<0.05)。由试验可得出,成熟培养液中单独添加15μg/mL的FSH和单独添加10μg/mL的LH浓度对延边黄牛卵母细胞体外成熟及重组胚后期发育效果最好;使用最佳浓度进行协同作用时,其共同作用要好于单独使用的效果。     

Timing of preovulatory LH surge and ovulation in superovulated sheep are affected by follicular status at start of the FSH treatment.

The aims of this study were to evaluate the chronology of periovulatory events (oestrus behaviour, LH surge and ovulation) in 16 superovulated Manchega sheep and to determine whether follicular status at start of the FSH supply might affect their occurrence. Mean timing for onset of oestrus behaviour was detected at 28.1 +/- 0.7 h after sponge withdrawal; the preovulatory LH surge and ovulation started at 37.2 +/- 0.7 h and 65.4 +/- 0.7 h after progestagen withdrawal, respectively. The intervals between oestrus, LH surge and ovulation were affected by a high individual variability, which might be the cause for reported decreased efficiency in embryo production. Current results also addressed the role of follicular status at start of the superovulatory treatment on the preovulatory LH surge and the ovulation. The interval LH surge-ovulation was increased in ewes with a growing dominant follicle at starting the FSH treatment (32.3 +/- 0.9 vs 28.6 +/- 0.5 h, p < 0.05). The developmental stage of the largest follicle at starting the superovulatory treatment also affected occurrence of LH surge and ovulation; follicles in growing phase advanced the occurrence of the LH surge and ovulation when compared to decreasing follicles (33.0 +/- 1.0 vs 43.5 +/- 1.1 h, p < 0.05, for LH peak and 60.7 +/- 1.1 vs 72.8 +/- 1.2 h, p < 0.05, for ovulation). Thus, only ewes with growing follicles ovulated prior to 55 h after sponge withdrawal; conversely, no sheep with decreasing follicles ovulated earlier than 67 h, when an 85.7% of the ewes bearing growing follicles has ovulated at 63 h.     

Dynamics of the Equine Preovulatory Follicle and Periovulatory Hormones: What's New?

Recent studies (2005–2008) on the interrelationships among the preovulatory follicle and periovulatory circulating hormones are reviewed. Close temporal and mechanistic relationships occur between estradiol/inhibin and follicle-stimulating hormone (FSH), between estradiol and luteinizing hormone (LH), and between progesterone and LH. Estradiol from the dominant follicle forms a surge that reaches a peak 2 days before ovulation. Estradiol, as well as inhibin, has a negative effect on FSH, and estradiol has a negative effect on LH. When estradiol decreases, the negative effect diminishes and accounts for the beginning of an FSH increase and a transition from a slow to rapid increase in LH on the day of the estradiol peak. The decrease in estradiol and the reduction or cessation in the growth of the preovulatory follicle beginning 2 days before ovulation are attributable to the development of a reciprocal negative effect of LH on follicle estradiol production when LH reaches a critical concentration. The LH decrease after the peak of the LH surge on the day after ovulation is related to a negative effect of a postovulatory increase in progesterone. Measurable repeatability within mares between consecutive estrous cycles occurs during the preovulatory period in diameter of the ovulatory follicle and concentrations of LH and FSH. Hormone-laden follicular fluid passes into the peritoneal cavity at ovulation and transiently alters the circulating concentrations of LH and FSH. Double ovulations are associated with greater estradiol concentrations and reduced concentrations of FSH.     

FSH and LH concentrations preceding post-partum ovulation in the mare

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

Plasma concentrations of immunoreactive (ir)-inhibin, gonadotropins and steroid hormones during the ovulatory cycle of the duck

The present study was undertaken to determine changes in circulating levels of immunoreactive (ir)-inhibin, FSH, LH, estradiol-17beta, progesterone, and testosterone during the ovulatory cycle of Shao ducks. Serial blood samples were taken from two groups of laying ducks for measurement of ir-inhibin, gonadotropins, and steroid hormones at 2 h intervals for 24 h. Plasma concentrations of ir-inhibin did not change significantly during the ovulatory cycle. The highest level of plasma ir-inhibin was observed 6 h prior to ovulation, which coincided with a decreased level of plasma FSH. One FSH surge was found 12 h after ovulation. Estradiol-17beta, progesterone, and testosterone were also determined during the ovulatory cycle. Two peak values were detected for estradiol-17beta 8 h before ovulation and 4 h after ovulation, while progesterone started to increase 4 h before ovulation and reached a peak at ovulation. The highest level of plasma testosterone was detected around the time of ovulation. These results suggest that inhibin may be involved in the control of FSH secretion during the ovulatory cycle. In addition, both LH and progesterone are of importance in the ovulation process of Shao ducks.     

Pituitary responsiveness to GnRH in mares following deslorelin acetate implantation to hasten ovulation

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.     

发情旺季母水牛生殖激素水平变化的研究

为了研究发情旺季母水牛生殖激素水平的变化规律,试验采用酶联免疫分析方法(ELISA)测定了发情周期血样中的促卵泡素(FSH)、促黄体素(LH)、雌二醇(E2)和孕酮(P4)4种激素,并分析了这些生殖激素在发情周期中的变化规律。结果表明:血清中FSH和LH的含量均由排卵前的第4天开始缓慢上升,排卵前达到峰值,在排卵后又明显下降;E2的含量在排卵前1天出现峰值,在排卵后第9天又出现1个小波峰;P4的含量在排卵后的第5天明显上升,第13天时达峰值,在排卵前3天出现最低水平。     

Effects of estradiol on gonadotrophin release, estrus and ovulation in CIDR-treated beef cattle

The effects of estradiol-17beta (E-17beta) or estradiol benzoate (EB) on gonadotrophin release, estrus and ovulation in beef cattle were evaluated in two experiments. In experiment 1, 16 ovariectomized cows received a previously used CIDR insert from days 0 to 7 and 1mg of EB on day 8; they also received 5mg of E-17beta on days 0 or 1, or 5mg of E-17beta+100mg of progesterone on day 0. There was only an effect of time (P<0.0001) on plasma concentrations of progesterone, estradiol, FSH, and LH. Following treatment with E-17beta, plasma FSH concentrations were suppressed for approximately 36 h, whereas plasma LH concentrations were reduced (P<0.05) for 6 h, but surged within 24 h. Injecting 1mg of EB 24 h after CIDR removal decreased (P<0.02) plasma LH concentrations for 6h, followed by an LH surge at 18 h. In experiment 2, ovary-intact heifers (n=40) received a used CIDR and 5mg of E-17beta+100mg of progesterone on day 0. On day 7, CIDR were removed, PGF given, and heifers received nothing (control) or 1mg of EB 12, 24, or 36 h later. In these groups, plasma LH peaked (mean+/-SEM) 78.0+/-23.0, 37.8+/-8.5, 44.4+/-10.3, and 51.0+/-5.1 h after CIDR removal (means, P<0.001; variances, P<0.001) and intervals from CIDR removal to ovulation were 102.0+/-6.7, 63.6+/-3.6, 81.6+/-3.5, and 78.0+/-4.1h (P<0.05). The interval from CIDR removal to ovulation was shorter and less variable in EB-treated groups; the interval from EB to ovulation was shortest (P<0.05) in the 12-h group. In summary, E-17beta or EB decreased both FSH and LH, but LH increased after 6h (despite elevated progesterone concentrations). Following CIDR removal, 1mg of EB effectively synchronized LH release, and ovulation (in intact cattle), but the interval from CIDR removal to EB treatment affected the time of ovulation.     

Plasma gonadotropins and ovarian hormones during the estrous cycle in high compared to low ovulation rate gilts

Mature gilts classified by low (12 to 16 corpora lutea [CL], n = 6) or high (17 to 26 CL, n = 5) ovulation rate (OR) were compared for plasma follicle-stimulating hormone (FSH), luteinizing hormone (LH), progesterone, estradiol-17beta, and inhibin during an estrous cycle. Gilts were checked for estrus at 8-h intervals beginning on d 18. Blood samples were collected at 8-h intervals beginning on d 18 of the third estrous cycle and continued for one complete estrous cycle. Analysis for FSH and LH was performed on samples collected at 8-h intervals and for ovarian hormones on samples collected at 24-h intervals. The data were standardized to the peak of LH at fourth (d 0) and fifth estrus for the follicular phase and analyzed in discrete periods during the periovulatory (-1, 0, +1 d relative to LH peak), early-luteal (d 1 to 5), mid-luteal (d 6 to 10), late-luteal (11 to 15), periluteolytic (-1, 0, +1 d relative to progesterone decline), and follicular (5 d prior to fifth estrus) phases of the estrous cycle. The number of CL during the sampling estrous cycle was greater (P < 0.005) for the high vs low OR gilts (18.8 vs 14.3) and again (P < 0.001) in the cycle subsequent to hormone measurement (20.9 vs 14.7). For high-OR gilts, FSH was greater during the ovulatory period (P = 0.002), the mid- (P < 0.05) and late-luteal phases (P = 0.01), and tended to be elevated during the early-luteal (P = 0.06), but not the luteolytic or follicular periods. LH was greater in high-OR gilts during the ovulatory period (P < 0.005), but not at other periods during the cycle. In high-OR gilts, progesterone was greater in the mid, late, and ovulatory phases (P < 0.005), but not in the follicular, ovulatory, and early-luteal phases. Concentrations of estradiol-17beta were not different between OR groups during the cycle. Inhibin was greater for the high OR group (P < 0.005) during the early, mid, late, luteolytic, and follicular phases (P < 0.001). The duration of the follicular phase (from last baseline estrogen value to the LH peak) was 6.5 +/- 0.5 d and was not affected by OR group. These results indicate that elevated concentrations of both FSH and LH are associated with increased ovulation rate during the ovulatory phase, but that only elevated FSH during much of the luteal phase is associated with increased ovulation rate. Of the ovarian hormones, both inhibin and progesterone are highly related to greater ovulation rates. These findings could aid in understanding how ovulation rate is controlled in pigs.     

Use of Equine Chorionic Gonadotropin to Control Reproduction of the Dairy Cow: A Review

Equine chorionic gonadotropin (eCG) is a member of the glycoprotein family of hormones along with LH, FSH and thyroid‐stimulating hormone. In non‐equid species, eCG shows high LH‐ and FSH‐like activities and has a high affinity for both FSH and LH receptors in the ovaries. On the granulosa and thecal cells of the follicle, eCG has long‐lasting LH‐ and FSH‐like effects that stimulate oestradiol and progesterone secretion. Thus, eCG administration in dairy cattle results in fewer atretic follicles, the recruitment of more small follicles showing an elevated growth rate, the sustained growth of medium and large follicles and improved development of the dominant and pre‐ovulatory follicle. In consequence, the quality of the ensuing CL is improved, and thereby progesterone secretion increased. Based on these characteristics, eCG treatment is utilized in veterinary medicine to control the reproductive activity of the cow by i) improving reproductive performance during early post‐partum stages; ii) increasing ovulation and pregnancy rates in non‐cyclic cows; iii) improving the conception rate in cows showing delayed ovulation; and finally, iv) eCG is currently included in protocols for fixed‐time artificial insemination since after inducing the synchrony of ovulation using a progesterone‐releasing device, eCG has beneficial effects on embryo development and survival. The above effects are not always observed in cyclic animals, but they are evident in animals in which LH secretion and ovarian activity are reduced or compromised, for instance, during the early post‐partum period, under seasonal heat stress, in anoestrus animals or in animals with a low body condition score.     

Endocrine and ovarian changes in response to the ram effect in medroxyprogesterone acetate-primed Corriedale ewes during the breeding and nonbreeding season

Two experiments were performed to determine the endocrine and ovarian changes in medroxyprogesterone acetate (MAP)-primed ewes after ram introduction. Experiment 1 was performed during the mid-breeding season with 71 ewes primed with an intravaginal MAP sponge for 12 days. While the control (C) ewes (n = 35) were in permanent contact with rams, the ram effect (RE) ewes (n = 36) were isolated for 34 days prior to contact with rams. At sponge withdrawal, all ewes were joined with eight sexually experienced marking Corriedale rams and estrus was recorded over the next 4 days. The ovaries were observed by laparoscopy 4-6 days after estrus. Four weeks later, pregnancy was determined by transrectal ultrasonography. In eight ewes from each group, ovaries were ultrasonographically scanned; FSH, LH, and estradiol-17beta were measured every 12 hours until ovulation or 96 hours after estrus. The response to the rams was not affected by the fact that ewes had been kept or not in close contact with males before teasing. No differences were found in FSH, LH, estradiol-17beta concentrations, growth of the ovulatory follicle, onset of estrus, ovulation rate, or pregnancy rate. Experiment 2 was performed with 14 ewes during the nonbreeding season. Ewes were isolated from rams for 1 month, and received a 6-day MAP priming. Ovaries were ultrasonographically scanned every 12 hours, and FSH, LH, estradiol-17beta, and progesterone were measured. Ewes that ovulated and came into estrus had higher FSH and estradiol-17beta levels before introduction of the rams than did ewes that had a silent ovulation. The endocrine pattern of the induced follicular phase of ewes that came into estrus was more similar to a normal follicular phase, than in ewes that had a silent ovulation. The follicle that finally ovulated tended to emerge earlier and in a more synchronized fashion in those ewes that did come into estrus. All ewes that ovulated had an LH surge and reached higher maximum FSH levels than ewes that did not ovulate, none of which had an LH surge. We conclude that (a) the effect of ram introduction in cyclic ewes treated with MAP may vary depending on the time of the breeding season at which teasing is performed; (b) patterns of FSH, and estradiol-17beta concentrations, as indicators of activity of the reproductive axis, may be used to classify depth of anestrus; and (c) the endocrine pattern of the induced follicular phase, which is related to the depth of anestrus, may be reflected in the behavioral responses to MAP priming and the ram effect.