补饲醋酸甲羟孕酮基础上分别进行前列腺素、N-甲基-D-天冬氨酸和来曲唑处理对母羊血浆繁殖激素水平的影响

试验旨在研究醋酸甲羟孕酮（medroxyprogesterone acetate,MPA）与前列腺素（prostaglandin,PG）、N-甲基-D-天冬氨酸（N-methyl-D-aspartate,NMDA）和来曲唑（letrozole,LE）的不同配伍对母羊血浆繁殖相关激素水平的影响。选取3岁经产萨福克母羊39只,平均体重（75.51±11.55） kg,随机均分为3组,试验Ⅰ组饲喂基础日粮+34 mg/（d·只） MPA+1 mL/只PG,试验Ⅱ组饲喂基础日粮+34 mg/（d·只） MPA+600 mg/（d·只） NMDA,试验Ⅲ组饲喂基础日粮+34 mg/（d·只） MPA+14 mg/（d·只） LE,试验期18 d。结果发现,补饲MPA基础上进行PG处理,母羊血浆中FSH水平呈极显著升高（P<0.01）;补饲MPA基础上进行NMDA处理,母羊血浆中E2、MLT、FSH和LH水平均呈极显著升高（P<0.01）;补饲MPA基础上进行LE处理,母羊血浆中MLT、LH和T水平均呈极显著升高（P<0.01）。综合比较各生殖激素之间的关系及变化规律,在本试验条件下,建议MPA与NMDA和LE分别结合使用,可作为调控母羊繁殖性能的药品;且通过比较激素水平得出,MPA与NMDA组合效果最佳。     

褪黑素基础上补喂来曲唑和N-甲基-D-天冬氨酸对母羊血浆繁殖激素水平的影响

试验旨在研究反季节给繁殖母羊补喂褪黑素（melatonin,MLT）及在MLT基础上补喂来曲唑（letrozole,LE）和N-甲基-D-天冬氨酸（N-methyl-D-aspartate,NMDA）对母羊血浆繁殖相关激素水平的影响,为调控母羊发情药物的开发及应用提供新思路。试验选取40只（3.0±0.5）岁经产萨福克母羊（平均体重为76.23 kg±12.25 kg）随机分为4组,每组10只,分别为对照组和试验Ⅰ、Ⅱ、Ⅲ组,分别饲喂基础日粮、基础日粮+MLT 10 mg/（只·d）、基础日粮+MLT 10 mg/（只·d）+LE 7 mg/（只·d）、基础日粮+MLT 10 mg/（只·d）+LE 7 mg/（只·d）+NMDA 300 mg/（只·d）。结果显示,与对照组相比,试验Ⅰ组母羊血浆中促卵泡素（FSH）、雌二醇（E₂）、雌三醇（E₃）及双氢睾酮（DHT）水平均极显著升高（P<0.01）,睾酮（T）水平显著降低（P<0.05）;试验Ⅱ组,母羊血浆MLT和LH水平均极显著升高（P<0.01）,FSH水平显著升高（P<0.05）;试验Ⅲ组,母羊血浆中MLT和促性腺激素释放激素（GnRH）水平均显著升高（P<0.05）。与试验Ⅰ组相比,试验Ⅱ组母羊血浆中MLT显著升高（P<0.05）,LH和T水平均极显著升高（P<0.01）。试验Ⅲ组与试验Ⅰ、Ⅱ组相比,FSH水平极显著降低（P<0.01）。综上所述,MLT和LE对母羊繁殖相关激素的释放有促进作用,且两者结合使用可达到调控母羊繁殖相关激素水平的效果;MLT、LE和NMDA组合应用对母羊繁殖激素调控效果不佳。     

褪黑素对体外培养绵羊垂体细胞分泌FSH和LH的影响

本文采用体外细胞培养和放射免疫测定法(RIA)的方法,研究了褪黑素(MLT)对季节性繁殖的蒙古母羊垂体细胞分泌促卵泡素(FSH)和促黄体素(LH)的作用。结果表明:当单独用递增的MLT(10、100、1000、2000pg/mL)处理原代垂体细胞时,随时间的延长FSH的分泌量极显著下降(P<0.01),但对LH的基础分泌没有影响;无论用10IU/mLhCG单独刺激,还是用不同剂量MLT与10IU/mLhCG共同刺激垂体细胞,FSH和LH的分泌都极显著高于对照组(P<0.01),但与MLT的剂量没有关系。     

复方中草药添加剂对辽宁绒山羊种公羊生殖激素的影响

将15只年龄(2.60±0.25)岁、体重(43.48±1.46)kg的辽宁绒山羊公羊随机分为3组,试验一组和试验二组分别饲喂10 g/d和15 g/d的复方中草药添加剂,对照组不喂,目的是研究中草药添加剂对种公羊促卵泡素、睾酮和促黄体素的影响。结果表明:试验一组在75 d后,精浆LH、FSH和T均显著(P<0.05)高于对照组,试验二组在75 d后,精浆FSH和T显著(P<0.05)高于对照组;在75 d后,两个试验组血浆FSH极显著(P<0.01)高于对照组,血浆LH、T显著(P<0.05)高于对照组。相关分析表明精浆T(y,ng/l)与LH(x,μg/l)存在显著相关关系,并且对照组、试验一组和试验二组拟合的对数曲线相似;对血浆进行同样分析表明,血浆以上两种激素的变化趋势与精浆相似;从曲线的位置分析试验一组T水平最高。这表明对于本复方中草药添加剂而言,辽宁绒山羊种公羊按照10 g/d的剂量应用即达到了提高生殖激素水平和生产性能的效果。     

α-Adrenergic control of gonadotropin secretion in the ewe

The effect of the centrally acting α-adrenoceptor agonist, clonidine, on plasma LH and FSH was studied in oestradiol-primed and unprimed ewes and in oestrous ewes. In unprimed anoestrous ewes, clonidine stimulated LH and FSH release after a lag period of 18 h, and noradrenaline intracarotid injection or i.v. infusions immediately stimulated LH release. In oestradiol-infused anoestrous ewes, clonidine produced either a delay or inhibition of the gonadotrophin surge and noradrenaline i.v. infusion advanced the LH surge. In oestrous ewes treated with clonidine, there was marked delay in the LH surge, but the magnitude of the LH and FSH surges were unaffected. Intravenous administration of α-adrenoceptor blockers, phentolamine and phenoxybenzamine, blocked the oestradiol-induced gondotrophin surge in anoestrous ewes. The effect of phenoxybenzamine on gonadotrophin surge was dose dependent in oestrous ewes. Small doses (4 mg/kg i.v.) of phenoxybenzamine delayed the synchronous LH and FSH surges. There was complete blockade of the LH surge and partial blockade of FSH surges in ewes given phenoxybenzamine (8 mg/kg i.v.) before the expected synchronous gonadotrophin surges. After this experiment, the initial rise of plasma progesterone concentrations did not occur until day 6 of oestrous cycle. Administration of phenoxybenzamine before the expected second FSH surge had no effect on the second FSH surge. Gonadotrophin release induced by gonadotrophin-releasing hormone was attenuated by phenoxybenzamine, but not by clonidine. The results suggest that the LH surge is under α-adrenergic control and the first FSH surge is under partial α-adrenergic control, but the second FSH surge is not under α-adrenergic control. The results also suggest oestradiol modulation of α-adrenergic receptor action.     

地塞米松和饲粮能量水平对肉仔鸡能量采食及神经肽Y基因表达的影响

本试验旨在探讨注射地塞米松(DEX)模拟应激状态下,应激和饲粮能量水平对肉仔鸡能量采食的影响。选取体重相近的180只23日龄的雄性爱拔益加(AA)肉鸡随机分成6组,每组3个重复,每个重复10只鸡。试验采用2×3析因设计,因素为DEX[处理(注射DEX2 mg/kg)、未处理(注射等剂量生理盐水)]和饲粮能量水平[高能(HE)、低能(LE)以及高能、低能自由采食(H-LE)]。预试期5 d,正试期7 d。结果表明:1)DEX处理极显著降低了肉仔鸡的采食量和体增重(P<0.01),极显著提高了耗料增重比、耗能增重比、腹脂率以及血浆葡萄糖、甘油三酯和尿酸的浓度(P<0.01),显著提高了肠道指数(P<0.05)。2)采用LE饲粮体增重(P<0.05)、腹脂率(P<0.01)显著低于其他2种饲粮,耗料增重比显著低于HE饲粮(P<0.05);采用HE饲粮耗能增重比极显著高于其他2种饲粮(P<0.01);采用H-LE饲粮神经肽Y(NPY)基因表达量显著高于LE饲粮(P<0.05)。3)DEX、饲粮能量水平对耗料增重比(P<0.05)和耗能增重比(P<0.01)的影响存在显著的互作效应。结果提示,DEX应激可使肉仔鸡血浆中葡萄糖、尿酸和甘油三酯的浓度升高;DEX应激和HE饲粮均能增加脂肪在腹部沉积,提高耗料增重比和耗能增重比;H-LE饲粮能上调肉仔鸡下丘脑NPY基因表达。     

Effect of dietary energy, body condition and calf removal on pituitary gonadotropins, gonadotropin-releasing hormone (GnRH) and hypothalamic opioids in beef cows

Beef cows (n = 64) were slaughtered to evaluate effects of dietary energy and calf removal (CR) on hypothalamic and adenohypophysial endocrine characteristics. From d 190 of gestation until parturition, cows received maintenance (ME; n = 32) or low (LE; n = 32) energy diets (ME = 100%, LE = 70% NRC recommendations). After parturition, half (n = 16) of each prepartum diet group received low (LE; n = 32) or high (HE = 130% NRC; n = 32) energy diets. At 30 d postpartum, cows were slaughtered 0 or 48 hr after CR. Hypothalami [preoptic area (POA), hypothalamus (HYP), stalk-median eminence (SME)] and pituitaries were collected. Basal and K(+)-induced release of GnRH from SME, and pituitary luteinizing hormone (LH) and follicle stimulating hormone (FSH) did not differ among groups (P greater than .05). Hypophyseal LH was correlated (P less than .01) with body condition score (BCS) at parturition and slaughter (r = .36 and .47, respectively). Prepartum LE diet increased (P less than .05) met-enkephalin in POA compared to prepartum ME (.59 +/- .05 vs. .44 +/- .04 pmol/mg) regardless of postpartum diet or suckling status. Concentrations of beta-endorphin in combined HYP + POA were decreased (P less than .05) by 48 hr CR (15.1 +/- 1.1 vs. 18.1 +/- 0.7 fmol/mg).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of Oxytropis glabra DC Poisoning on the Reproductive Organs in Hetian Sheep Ewes

The study was aimed to research the effects of Oxytropis glabra DC (O.glabra DC) poisoning on reproductive organs coefficent, reproductive performance and related gene expression in Hetian sheep ewes. The sera, hypothalamus, pituitary and ovary of Hetian sheep ewes cases poisoning of O. glabra DC were collected, the organ exponent and contents of GnRH, FSH, LH, E₂ and P₄ in serum were measured, then the mRNA expression of reproductive genes were measured. The result demonstrated that the index of hypothalamus, pituitary and ovary were extremely significantly higher than normal sheep (P < 0.01),the follicle number on the surface of the ovaries in poisoning groups were significantly lower than normal sheep (P < 0.05). The result of hematoxylin-eosin staining showed that the nuclear of neuronal cells in hypothalamus were pyknosis and hyperchromatic; The nuclear of cells in pituitary deformation and hyperchromatic, cytoplasm decreased; The primary oocyte in ovary dissolved, disappeared, interstitial blood vessel expanded. The content of GnRH, FSH, LH, E₂ and P₄ in serum in poisoned Hetian sheep ewes were extremely significantly lower than normal sheep (P < 0.01). The mRNA expression levels of Kiss-1, GPR54, ERα in hypothalamus, GnRHR in pituitary and FSHR and LHR in ovary were extremely significantly lower than normal sheep (P < 0.01). The result showed that O. glabra DC poisoning could affect Hetian sheep ewes reproductive system by affecting microstructure and ultrastructure of hypothalamus-pituitary-ovarian axis.     

小花棘豆中毒对和田羊母羊繁殖器官的影响

试验旨在探讨小花棘豆（Oxytropis glabra DC）中毒对和田羊母羊繁殖器官指数、性激素水平和相关基因mRNA表达量的影响。以小花棘豆中毒和田羊母羊为研究对象,采集血清后屠宰,采集试验羊的丘脑、垂体和卵巢组织,测定其脏器系数,检测血清中促性腺激素释放激素（GnRH）、促卵泡素（FSH）、促黄体素（LH）、雌二醇（E₂）和孕酮（P₄）含量的变化,并检测各组织中相关繁殖基因的表达。结果显示,小花棘豆中毒和田羊母羊丘脑、垂体和卵巢指数均极显著升高（P < 0.01）,且卵巢表面卵泡数显著下降（P < 0.05）,HE染色表明丘脑神经元细胞固缩、浓染;垂体中细胞核变形、浓染,胞浆减少;卵巢中初级卵母细胞溶解、消失,间质血管扩张。小花棘豆中毒和田羊母羊血清中GnRH、FSH、LH、E₂和P₄含量均极显著下降（P < 0.01）,丘脑中Kiss-1、GPR54、ERα mRNA,垂体中GnRHR mRNA和卵巢中FSHR、LHR mRNA表达量均极显著下降（P < 0.01）。结果表明,小花棘豆毒性成分可通过丘脑-垂体-性腺轴影响和田羊母羊的生殖系统。     

纳米载铜蒙脱石对生长肥育猪生产性能

摘要：试验旨在研究日粮中添加纳米载铜蒙脱石对生长育肥猪生产性能及血液生化指标的影响。选取72头健康“杜×大×长”三元杂交断奶仔猪,随机分为3组,每组3个重复,每个重复8头(公母各半)。分别饲喂基础日粮（对照组）、基础日粮+20 mg/kg泰乐菌素+100 mg/kg磺胺二甲基嘧啶(SM2)（试验Ⅰ组）和基础日粮+1500 mg/kg纳米载铜蒙脱石（MMT-Cu）（试验Ⅱ组）。比较研究MMT-Cu和泰乐菌素＋磺胺二甲基嘧啶对生长肥育猪生产性能及血液生化指标的影响。结果表明,与对照组和试验Ⅰ组相比,试验Ⅱ组料重比、血清ALB、SUN、Ch、TP含量极显著下降(P<0.01);血钙含量、GTP活性极显著提高（P<0.01）;TP和GLU含量显著下降 (P<0.05)。因此,纳米载铜蒙脱石提高了生长肥育猪的料重比,并对血清中ALB 、Ca、GPT、SUN、TG、Ch、TP、GLU均产生不同程度的影响。     

小尾寒羊高繁殖力和常年发情内分泌机理的研究

本研究对5只小尾寒羊成年母羊以及相同条件下的5只细毛羊成年母羊用导管法采血,用放射免疫分析法测定血浆中FSH和LH浓度.试情公羊爬跨法鉴定结果表明,小尾寒羊具有显著的非季节性发情特性.小尾寒羊各月份、4个季节和全年的血浆FSH和LH浓度均极显著高于(P＜0.0001)低繁殖力和季节性发情的细毛羊.小尾寒羊发情期血浆FSH和LH的基础浓度、峰值、谷值、排卵前峰值均显著高于(P＜0.05～P＜0.0001)细毛羊的.发情期间小尾寒羊和细毛羊FSH分泌呈现2个明显的峰,第一个峰与排卵前LH峰并存,第二个FSH峰出现在发情后1d.小尾寒羊FSH二次峰均值极显著高于(P＜0.01)细毛羊的.本研究结果提示FSH和LH基因可作为小尾寒羊高繁殖力的候选基因来加以研究.     

甘草次酸对青年母猪生长性能、抗氧化能力及生殖激素浓度的影响

本试验旨在研究甘草次酸对青年母猪生长性能、抗氧化能力及生殖激素浓度的影响。选用(124±7)日龄、平均体重为(61.00±3.03)kg的健康长×大二元青年母猪64头,按日龄、体重相近的原则随机分为4个组,分别为对照组(基础饲粮)、玉米赤霉烯酮组(基础饲粮+1 mg/kg玉米赤霉烯酮)、甘草次酸组(基础饲粮+400 mg/kg甘草次酸),玉米赤霉烯酮+甘草次酸组(基础饲粮+1 mg/kg玉米赤霉烯酮+400 mg/kg甘草次酸),每组4个重复,每个重复4头母猪。预试期5 d,正试期28 d。结果表明:1)与对照组相比,玉米赤霉烯酮组青年母猪阴户发育异常,阴户长、宽及面积极显著增加(P<0.01)。2)甘草次酸组和玉米赤霉烯酮+甘草次酸组青年母猪的平均日采食量和平均日增重均显著高于对照组和玉米赤霉烯酮组(P<0.05)。3)与对照组相比,玉米赤霉烯酮组青年母猪的粗脂肪消化率显著增加(P<0.05),钙和磷消化率显著降低(P<0.05);甘草次酸组的粗纤维和粗脂肪消化率显著增加(P<0.05),钙和磷消化率极显著增加(P<0.01);玉米赤霉烯酮+甘草次酸组的粗脂肪消化率显著增加(P<0.05)。4)与对照组相比,玉米赤霉烯酮组青年母猪的血清吻素(Kp)、雌二醇(E2)、促黄体素(LH)浓度极显著增加(P<0.01),甘草次酸组的血清Kp和E2浓度显著增加(P<0.05),玉米赤霉烯酮+甘草次酸组的血清Kp、E2和LH浓度极显著增加(P<0.01)。5)玉米赤霉烯酮组青年母猪的血清丙二醛(MDA)含量显著高于对照组和甘草次酸组(P<0.05);与玉米赤霉烯酮组相比,玉米赤霉烯酮+甘草次酸组的血清MDA含量显著降低(P<0.05),血清乳酸脱氢酶(LDH)活性极显著降低(P<0.01)。综上所述,饲粮中添加甘草次酸可改善青年母猪的生长性能和抗氧化能力,影响生殖激素浓度,具有缓解玉米赤霉烯酮对青年母猪繁殖危害的作用。     

小尾寒羊FSHβ和LHβ基因在生殖轴的表达研究

为揭示FSHβ和LHβ基因在小尾寒羊下丘脑-垂体-卵巢轴(HPOA)中的表达规律,深入了解其对小尾寒羊多羔的作用,本研究采用实时荧光定量PCR技术对6只小尾寒羊(FecB++型单、多羔羊各3只)的生殖组织及脑组织中FSHβ和LHβ基因的表达差异进行分析。结果表明:FSHβ和LHβ基因在大脑、小脑、下丘脑、卵巢、子宫、输卵管和垂体7种组织中均有表达,FSHβ主要在小尾寒羊下丘脑和卵巢高表达,LHβ在垂体高表达;FSHβ基因在小尾寒羊多羔群体下丘脑、卵巢、子宫、输卵管、垂体的表达极显著高于单羔群体(P<0.01),LHβ基因在小尾寒羊多羔群体下丘脑、卵巢、子宫、输卵管、垂体、小脑、大脑表达量均极显著高于单羔群体(P<0.01)。研究结果提示,FSHβ和LHβ基因可能参与小尾寒羊多羔性状调控。     

不同能量水平对母羊繁殖性能的影响

在高、中、低(18.99、14.48、8.81MJ/d)3个不同能量水平饲养条件下,对36只杂交母羊(萨福克♂×小尾寒羊♀)的体重变化,黄体数及激素FSH、LH分泌情况进行了研究分析。结果表明:高能量组的试验羊平均日增重比低能组和中等能量组分别提高235.5g(/(只·d)(P<0.05)、70.6g(/只·d)(P<0.05),黄体数分别增加81.3%(P<0.05)、43%(P>0.05)。同时,低能量组FSH、LH激素水平高于中等能量和高能量组,说明日粮能量水平影响母羊卵泡发育,排卵及黄体形成。     

Luteinizing hormone, follicle stimulating hormone and prolactin secretion in ewes and wethers after zeranol or estradiol injection

Plasma concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (PRL) were determined over a 24-h period using radioimmunoassay in sheep injected with corn oil (control) or various doses of zeranol or estradiol-17 beta. Injection of .333, 1 or 10 mg of zeranol caused dose-related increases (P less than .01) in plasma PRL (peak levels at 12 to 18 h) and LH (peak levels at 12 to 20 h) in ovariectomized ewes. Similarly, PRL and LH increased following doses of 33 or 100 microgram of estradiol. Before the LH surge, plasma LH levels were significantly depressed (4 to 8 h). Plasma FSH levels were significantly decreased 4 to 8 h after zeranol and estradiol injection. Slight surges of FSH were observed at times similar to those of LH, but the peak level was never greater than control levels. Injection of 1 mg of zeranol or 100 microgram of estradiol into wethers resulted in a 24-h pattern of PRL secretion not significantly different of LH concentration and significantly prolonged inhibition of FSH secretion. These results indicate similarities in the effects of zeranol and estradiol on anterior pituitary hormone secretion within groups of animals of the same sex or reproductive state. Differences in secretion and plasma concentrations of LH, FSH and PRL due to underlying sexual dimorphism are maintained and expressed even when animals are challenged with structurally different compounds of varying estrogenic potencies.     

Increased ovulation rate of adult ewes treated with anti-bovine LH antiserum during the normal breeding season

Adult Suffolk ewes (n = 14) were treated on d 10 of the estrous cycle with anti-bovine luteinizing hormone (LH) antiserum. Control ewes (n = 10) were treated with normal horse serum. Estrous behavior and the number of corpora lutea and ovarian follicles were examined at the subsequent estrous cycle. Daily plasma concentrations of progesterone (P4), follicle stimulating hormone (FSH) and estradiol were determined before and after treatment. Ewes treated with antiserum had a higher (P less than .05) ovulation rate (2.7 +/- .2) than did controls (2.1 +/- .1). No differences were found in the numbers of large (greater than 5 mm) or small (less than 5 mm) follicles between treatment groups. Estrus was delayed (P less than .025) approximately .6 d/in ewes treated with antisera. Immunoreactive FSH increased (P less than .05) within 1 d after treatment and remained higher than the controls for 5 d. Peak estradiol concentrations occurred on d 17 for treated ewes compared with peak concentrations on d 15 or 16 for control ewes. The P4 concentrations were generally less (P less than .025) in treated ewes throughout the luteal phase of the treatment cycle. These data demonstrate that ovulation rate is increased in ewes treated with LH antiserum. The marked increase in plasma FSH suggests a possible mechanism whereby ovulation rate is enhanced.     

甜菜碱提高蛋鸡产蛋性能的机理研究

15 36只 30 0日龄罗曼蛋鸡 ,随机分为 4组 ,分别饲喂添加 0 ,5 0 0 ,10 0 0 ,15 0 0mg/kg甜菜碱的玉米—豆粕型日粮 ,研究甜菜碱提高蛋鸡产蛋性能的作用机制。结果表明 ,日粮中添加 10 0 0mg/kg甜菜碱对提高蛋鸡产蛋性能效果最佳 ,显著提高产蛋率 10 .11% (P <0 .0 5 ) ,提高饲料转化率 6 .4 1% (P <0 .0 5 )。进一步研究发现 ,日粮中添加 10 0 0mg/kg甜菜碱使血清促卵泡生成素 (FSH)、促黄体生成素 (LH)、极低密度脂蛋白胆固醇含量和脂肪酶活性分别升高了 5 6 .4 9%(P <0 .0 1)、86 .0 3% (P <0 .0 5 )、4 3.0 7% (P <0 .0 5 )和 30 .0 7% (P <0 .0 5 ) ,血清甘油三酯和尿酸含量分别下降了 2 2 .18%(P <0 .0 5 )、18.6 6 % (P <0 .0 5 )。上述结果提示 :甜菜碱通过增强腺垂体FSH和LH的分泌 ,同时促进卵蛋白和卵脂肪沉积 ,从而提高蛋鸡产蛋率和饲料利用率     

Adenohypophyseal function in bitches treated with medroxyprogesterone acetate

The aim of this study was to investigate the effects of treatment with medroxyprogesterone acetate (MPA) on canine adenohypophyseal function. Five Beagle bitches were treated with MPA (10mg/kg, every 4 weeks) and their adenohypophyseal function was assessed in a combined adenohypophyseal function test. Four hypophysiotropic hormones (CRH, GHRH, GnRH, and TRH) were administered before and 2, 5, 8, and 11 months after the start of MPA treatment, and blood samples for determination of the plasma concentrations of ACTH, cortisol, GH, IGF-1, LH, FSH, prolactin, alpha-MSH, and TSH were collected at -15, 0, 5, 10, 20, 30, and 45 min after suprapituitary stimulation. MPA successfully prevented the occurrence of estrus, ovulation, and a subsequent luteal phase. MPA treatment did not affect basal and GnRH-induced plasma LH concentrations. The basal plasma FSH concentration was significantly higher at 2 months after the start of MPA treatment than before or at 5, 8, and 11 months after the start of treatment. The maximal FSH increment and the AUC for FSH after suprapituitary stimulation were significantly higher before treatment than at 5, 8, and 11 months of MPA treatment. Differences in mean basal plasma GH concentrations before and during treatment were not significant, but MPA treatment resulted in significantly elevated basal plasma IGF-1 concentrations at 8 and 11 months. MPA treatment did not affect basal and stimulated plasma ACTH concentrations, with the exception of a decreased AUC for ACTH at 11 months. In contrast, the maximal cortisol increment and the AUC for cortisol after suprapituitary stimulation were significantly lower during MPA treatment than prior to treatment. MPA treatment did not affect basal plasma concentrations of prolactin, TSH, and alpha-MSH, with the exception of slightly increased basal plasma TSH concentrations at 8 months of treatment. MPA treatment did not affect TRH-induced plasma concentrations of prolactin and TSH. In conclusion, the effects of chronic MPA treatment on adenohypophyseal function included increased FSH secretion, unaffected LH secretion, activation of the mammary GH-induced IGF-I secretion, slightly activated TSH secretion, suppression of the hypothalamic-pituitary-adrenocortical axis, and unaffected secretion of prolactin and alpha-MSH.     

Enzyme Immunoassays for the Determination of Ovine LH and FSH

The development of competitive enzyme immunoassays for ovine plasma LH (oLH) and FSH (oFSH) is described. Standards and plasma samples were preincubated with diluted antiserum to oLH or oFSH and the reacted solution (100 μl per well) was transferred to plates previously coated with oLH or oFSH, respectively. The second antibody used was anti‐rabbit IgG horseradish peroxidase. The measuring range was 0.39–50 ng/ml for each hormone and the 50% relative binding sensitivity was 9 ng/ml for oLH. The respective value for oFSH was 3.5 or 34 ng/ml with different hormone and antibody preparations used for the assay. The enzyme immunoassays were used to determine oLH and oFSH levels in plasma from ewes of two breeds during the oestrous cycle. The assays detected the first FSH surge coincident with the LH surge, the second FSH surge about 24 h later and the periodic fluctuations of FSH concentrations during the luteal phase of the oestrous cycle. These enzyme immunoassays are an efficient and economic alternative to the established radioimmunoassays (RIA) for oLH and oFSH.     

Effect of exogenous oestradiol and lighting regime on age at first egg in domestic pullets

1. Groups of ISA Brown pullets were transferred from 8- to 16-h photoperiods at 34, 44 or 54 d. In each group, 12 birds were injected on alternate days over a 12-d period starting 6 d before the change in photoperiod with beta-oestradiol-3-benzoate (1 mg/kg body weight) or with arachis oil vehicle (controls). Short-day controls were similarly injected from 28 to 40 d. Long-day (16 h) controls were also included in the trial but were not injected. Age at first egg (AFE) was recorded and plasma luteinising hormone (LH) concentrations were measured around the time of oestradiol treatment. 2. Mean AFE for birds photostimulated at 34 d was not significantly different from short-day controls. Birds photostimulated at 44 and 54 d matured at similar ages but 3 weeks earlier than short-day controls (P<0.05). 3. There was a tendency for oestradiol to advance AFE for birds photostimulated at 34 d (P=0.15) but to delay AFE following photostimulation at 44 d (P=0.23). Oestradiol significantly delayed AFE for the birds photostimulated at 54 d (P=0.01). 4. Plasma LH levels during 6 d of oestradiol injection but before transfer from 8- to 16-h photoperiods tended to fall between 28 and 34 d, were relatively constant between 38 and 44 d, but declined significantly between 48 and 54 d. Following photostimulation at 34 d, increases in plasma LH levels for oestradiol-injected birds were significantly greater than for controls. Oestradiol treatment had no significant effect on changes in plasma LH concentrations after photostimulation at 44 or 54 d. 5. This trial confirms previous work showing that pullets are unresponsive to photostimulation before 6 weeks of age. It also demonstrates that raising circulating oestrogen levels by injecting 0.5 mg/kg oestradiol benzoate on alternate days enhances the LH response to photostimulation at 34-d, but only very slightly sensitises a 34-d old bird to an increase in photoperiod which, 10 d later, is capable of advancing AFE in control birds by 24 d. Increased circulating oestrogen might be a factor which allows pullets to advance AFE in response to an increase in daylength.