初情期前母猪垂体细胞LH和FSH的释放及其对GnRH类似物的反应

利用垂体细胞单层培养模型研究了30，60，90，120和150日龄北京黑猪母猪垂体细胞LH和FSH的释放及其对LRH－A3反应能力。结果表明，猪垂体细胞LH和FSH释放对LRH－A3的反应呈S形剂量依赖型同线。LH基础释放量和LRH－A3刺激的最大释放量在不同日龄间没有显著差异，说明初情期前母猪垂体细胞已达最大LH释放和对GnRH反应的能力。FSH的基础释放量和LRH－A3刺激的最在释放量在30日龄与60日龄之间无差异，但90日龄以后垂体细胞FSH的释施量随日龄增大而降低，提出可能由于垂体在体内时受过抑制素的作用。     

能量影响初情期前母猪生殖机能的机理

日粮能量通过代谢激素:生长激素、胰岛素、瘦素(Leptin)、甲状腺素、IGF-Ⅰ以及葡萄糖等代谢信号为媒介,影响垂体促性腺激素分泌;此外,也可直接作用于卵巢,影响性腺激素分泌及卵巢发育。能量负平衡时,GH脉冲的频率和振幅提高,而血浆IGF-Ⅰ被抑制。Leptin浓度在短期限饲或禁饲时都低于正常组。胰岛素及Leptin在初情期前母猪生殖机能有重要作用,胰岛素是营养代谢与母猪生殖机能相互作用的一个媒介,IGF能够长期影响母猪生殖机能,甲状腺激素对初情期前母猪生殖机能有影响,因此能量通过代谢激素影响初情期前母猪生殖机能。     

短期限饲对初情期前母猪和初产母猪繁殖机能的影响

作者探讨短期限饲对初情期前母猪和初产母猪繁殖机能的影响及其机理。当体重和脂肪与肌肉比例无变化,短期限饲影响初情期前母猪卵巢繁殖功能。葡萄糖和胰岛素在初情期前母猪繁殖机能中有重要作用。胰岛素是营养与繁殖之间的一个媒介。无内源性激素影响时,短期限饲调节卵巢繁殖功能。在限饲期间,促性腺激素在白天出现明显节奏性释放。短期限饲通过胰岛素影响初产母猪卵泡发育、断奶后发情间隔和排卵率。胰岛素是营养与胚胎存活率之间的介质。短期限饲由于限饲时间不同对初产母猪胚胎存活率影响也不同。分析营养与繁殖机能关系,调节营养使母猪发挥最大繁殖潜力,促进养猪业发展。     

日粮能量对初情期前母猪外周血清FSH、LH释放的影响

选杜长大三元杂交母猪24头(140日龄)分3个组,高能组、中能组、低能组。试验处理20 d,每5 d采血1次,离心,-20℃冰箱储存,然后放射免疫分析(RIA)。结果表明:外周血浆FSH、LH浓度在不同日粮能量水平饲养后,高能组急剧上升,到第10天达到高峰,然后逐渐下降,在处理第20天接近恢复试验前水平。低能组缓慢降低,第10天到最低点,然后逐渐恢复,在处理第20天接近恢复试验前水平。外周血浆FSH、LH浓度在高能组与低能组于处理第5天差异显著(P<0.05),第10天差异极显著(P<0.01),说明能量通过下丘脑-垂体-卵巢轴影响初情期前母猪生殖机能。     

枫泾和长白母猪对初情期前注射黄体素释放激素类似物(LRH-A_2)的反应

进行两个试验,研究了初情期前不同日龄的枫泾和长白母猪LRH-A_2诱导的LH水平和不同剂量的LRH-A_2对LH水平的影响。结果表明,77日龄枫泾猪,85和202日龄长白猪在诱导前血清中LH含量分别为1.70±0.17、0.74±0.10和1.40±0.14ng/ml,前二者和后二者间的差异极为明显(P<0.001)。除枫泾猪的5μg和10μg剂量外,其余各剂量在注射5分钟后血清中LH含量均显著高于注射前的LH值(P<0.005～0.001)。枫泾猪诱导的LH峰值与LRH-A_2的剂量无关,而长白猪的峰值出现时间和峰值高低均因剂量而异。诱导的LH值随初情期前的小母猪日龄而变化。枫泾猪和长白猪诱导的LH峰值出现的日龄分别为30和60天,峰值分别为5.55±0.63和16.14±2.74ng/ml,差异极明显(P<0.005)。枫泾猪在30～60和75～90日龄时诱导的LH值分别显著低于长白猪在60和95日龄的诱导值,但接近初情期时,两猪种间的差异则变得不明显。可结论如下:甾体激素的负反馈机制,枫泾和长白猪分别在30和60日龄开始建立,并在初情期时达到完善。     

PG 600诱导初情期前母猪的同期发情及其对移植胚胎存活的影响

用PG600诱导初情期前的青年母猪同期发情,进行胚胎移植试验。结果是,有82.85%的母猪在经PG600处理后的第4天、第5天发情;胚胎移植后,怀孕率达到85.71%,头平均产仔6.79头,与对照组无显著差异(P>0.05)。     

能量对初情期前母猪类胰岛素样生长因子分泌的影响

日粮能量水平的变化会影响到体内循环与营养代谢相关的激素和因子,而这些激素和因子的变化可能会作为代谢信号对卵泡的发育产生影响,并对母猪初情期产生影响,这些代谢信号包括胰岛素样生长因子-I（IGF-I）。能量限饲时,母猪血清IGF-I浓度减少,营养减少,     

LRH－A_3诱导初情期前母猪发情排卵的效果和机理研究

本研究探讨了ＬＲＨ－Ａ３诱导初情期前北京黑猪发情排卵的效果及其内分泌机理。对６头１５０日龄母猪肌注ＬＲＨ－Ａ３，７５μｇ／头。在注射后０，１，２，３和４ｈ及注射后１，２，３和４ｄ采血测定ＬＨ、ＦＳＨ、Ｅ２和Ｐ４浓度。注射后１０ｄ取卵巢，根据卵巢上黄体数计算排卵率。结果表明：注射ＬＲＨ－Ａ３后，出现排卵和卵巢囊肿的母猪分别为４头（６６．７％）和２头（３３．７％）。４头排卵母猪中的３头和２头卵巢囊肿母猪中的１头有发情表现。排卵的母猪，分别在注射后１ｈ和３ｈ出现ＬＨ和ＦＳＨ峰；注射后２ｄＥ２浓度最高，３ｄ和４ｄＰ４浓度上升。发生卵巢囊肿的母猪，注射后１ｈ出现明显低于排卵母猪的ＬＨ峰，而ＦＳＨ浓度没有上升，Ｅ２和Ｐ４在３ｄ和４ｄ都增加。通过试验认为，初情期前母猪的卵巢对ＬＲＨ－Ａ３至少有两种反应，即排卵或卵巢囊肿。     

初情期前小母猪的超数排卵及胚胎发育研究

对25头3～4月龄小母猪超数排卵(简称超排),平均每头供体获得24.12枚卵子,这种小母猪的超排卵能正常受精,受精率达93.1%.受精卵在体内能经历正常的发育,约有89.5%的受精卵能发育至桑椹期以上胚胎.     

日粮能量对初情期前母猪胰岛素及生长激素分泌的影响

日粮能量水平对母猪的发情、受胎、胚胎发育和存活以及仔猪初生重和断奶重等繁殖性能有重要影响.试验研究能量影响初情期前母猪胰岛素及生长激素分泌变化,从而探明能量影响初情期前母猪生殖机能的机制,为生产提供依据.     

能量对蛋鸡卵巢促卵泡素受体mRNA表达及产蛋率的影响

为了探讨不同日粮能量水平对蛋鸡性成熟过程中卵巢促卵泡素受体(FSHR)mRNA表达及产蛋率的影响,试验选取360只体莺相近的8周龄海兰褐壳蛋鸡,采用单因素随机试验,随机分为5个组,每个组4个重复,每重复18只鸡.在蛋鸡采食其他营养成分相同的情况下,配制不同梯度的能量饲料,采用相对定量反转录-聚合酶链反应方法,测定蛋鸡性成熟过程中卵巢FSHR mRNA表达量.结果表明:高能组卵巢FSHR mRNA的表达量呈先升后降的趋势;对照组、低能组随周龄的增加鸡卵巢FSHR mRNA表达量逐渐增加.14周龄,低能Ⅱ组卵巢FSHR mRNA表达量显著低于其他4组(P<0.05);18周龄,对照组鸡卵巢FSHR mRNA表达量显著高于低能Ⅱ组(P<0.05),除对照组外的其他4组间差异不显著(P>0.05);22周龄,对照组与高能Ⅱ组和低能Ⅰ组间没有差异(P>0.05),却显著高于高能Ⅰ组和低能Ⅱ组(P<0.05).鸡22周龄卵巢FSHR mRNA表达量与22、28周龄产蛋率呈极显著正相关(P<0.01),与35周龄产蛋率呈显著正相关(P<0.05),而与46周龄产蛋率无显著相关(P>0.05).结果提示,适当的能量水平可以提高FSHR mRNA的表达,进而提高产蛋率.     

饲粮能量水平对后备母猪卵巢发育及相关基因表达的影响

本试验旨在研究饲粮能量水平对后备母猪卵巢发育及卵巢促卵泡素受体(FSHR)和促黄体素受体(LH/CGR)mRNA表达的影响。选择27头体重(61.0±3.1)kg的长×大二元母猪,随机分成3组(每组3个重复,每个重复3头猪),分别饲喂低、中、高3个能量水平[分别为NRC(1998)推荐消化能需要的90%、100%和110%]的饲粮。试验期内各组平均日采食量相同,但摄入的消化能水平不同。试验母猪在第2个发情期的第19天屠宰。结果表明:高能组卵巢重及大卵泡数显著高于低能组(P0.05);各组间小卵泡数量差异不显著(P0.05)。高能组卵巢FSHR和LH/CGR mRNA表达量最高,显著高于低能组(P0.05)。由此得出,高能量水平饲粮可促进后备母猪卵巢发育,有利于促进卵巢FSHR和LH/CGR mRNA的表达。     

Interaction of zearalenone and soybean isoflavone in diets on the growth performance, organ development and serum parameters in prepubertal gilts

The aim of the present research was to determine the interactive effect of zearalenone (ZEA) and soybean isoflavone (ISO) on the growth performance, development of organs and serum parameters in prepubertal gilts. Ninety 75-day-old female pigs (Duroc × Landrace × Yorkshire, 26.5 ± 0.60 kg) were randomly allocated to nine diet treatments during the 21-day study. The experiment employed a 3 × 3 factorial design using a non-soybean meal diet with the addition of 0, 0.5 or 2.0 mg/kg ZEA and 0, 300 or 600 mg/kg ISO. The results indicated that simultaneous addition of ZEA and ISO had no significant influence on the growth performance in prepubertal gilts. Zearalenone with 2 mg/kg increased (p < 0.05) the relative weight of the reproductive organs (including uterus and vagina) but had no obvious effects (p > 0.05) on the relative weight of the heart, liver, lung, kidney and spleen. Isoflavone at 600 mg/kg could offset the increased weight of the reproductive organs induced by ZEA. Simultaneous addition of ZEA and ISO to prepubertal gilts increased the level of alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase in the serum (p < 0.05) at day 14 but their levels decreased (p < 0.05) over time. Zearalenone increased the level of malondialdehyde and decreased the concentrations of superoxide dismutase and glutathione peroxidase (p < 0.05) in the serum. The results suggested that ISO added to diets at 600 mg/kg could reduce the increase in the relative weight of reproductive organs and relieve the oxidative stress induced by ZEA added at 2 mg/kg during the growth phase in prepubertal gilts.     

玉米赤霉烯酮对青年母猪子宫发育、生长激素分泌及其受体分布与表达的影响

本试验旨在研究玉米赤霉烯酮(ZEA)对青年母猪子宫发育、生长激素(GH)分泌及其受体(GHR)分布与表达的影响.选择胎次和体重[(23.20±0.68)kg]相近的长×大二元青年母猪48头,将其随机分为4组,每组12个重复,每个重复1头.对照组(CON组)饲喂基础饲粮,试验组(T1、T2、T3组)饲喂在基础饲粮中分别添...     

Effects of restriction of dietary energy intake during the prepubertal period on secretion of luteinizing hormone and responsiveness of the pituitary to luteinizing hormone-releasing hormone in heifers

The working hypothesis that a low plane of nutrition during the prepubertal period delays puberty in heifers by retarding the prepubertal increase in secretion of luteinizing hormone (LH) was investigated. Secretion of LH and the responsiveness of the pituitary to LH-releasing hormone (LHRH) were compared in heifers fed a growing diet (which allowed spontaneous occurrence of puberty; n = 12; control) or an energy deficient diet (which delayed puberty; n = 11; delayed) during the prepubertal period. The dietary treatments were initiated when the heifers were 299 +/- 14 (mean +/- SD) d of age (d 0 of the experiment) and continued until d 175 of the experiment (474 +/- 14 d of age). Weight gains were .79 +/- .05 (mean +/- SE) and .21 +/- .03 kg X head-1 X d-1 for control and delayed heifers, respectively. Puberty occurred on d 120 +/- 14 of the experiment (428 +/- 13 d of age) in control heifers, whereas none of the delayed heifers attained puberty during the feeding period. Serum concentration of LH and the frequency of LH pulses increased rapidly during the 175-d feeding period in control heifers. In delayed heifers, serum LH concentration increased less rapidly and no increase in pulse frequency was detected during the experimental period. Amplitude of LH pulses tended to be higher in control than delayed heifers. Responsiveness of LH secretion to LHRH was lower in delayed than control heifers. It is speculated that failure of secretion of LH to increase is the causative factor for delayed puberty when dietary energy is limited during the prepubertal period in heifers.     

Effects of dietary energy levels on plasma leptin in sheep

This experiment investigates the changes in the plasma leptin levels of sheep fed a diet of three energy levels (low, moderate and high). Four mature wethers were used for this experiment. For the first 4 weeks, the sheep were fed diets to provide 1.2 times the maintenance metabolizable energy requirements, low energy levels (LE). During the second 4 weeks, the sheep were fed diets to provide 1.5 times the maintenance metabolizable energy requirements, moderate energy levels (ME). During third 4‐week period, the sheep were fed a diet to provide 1.8 times the maintenance metabolizable energy requirements, high energy levels (HE). Body weight was determined every week. Blood samples were collected prior to the morning meal at 3 days intervals throughout the experiment, and plasma leptin, insulin and nonesterified fatty acid (NEFA) concentrations were assayed. Body weight decreased in week 1 after the start of the experiment, it continued to decrease during the LE feeding, but it gradually increased until the end of HE period. Similarly, plasma leptin concentration decreased during LE feeding, but increased during the HE feeding. Additionally, positive correlation was obtained between leptin and insulin or glucose concentrations, whereas no clear relationship with circulating NEFA was observed. In conclusion, it was suggested that plasma leptin concentrations were affected by the metabolizable energy in feed.     

特种野母猪适宜日粮结构与能量水平的研究

试验研究不同日粮结构和能量水平对后备期特种野母猪饲料养分消化率、血清生化指标的影响。通过采用2(日粮结构)×4(能量水平)因子设计,选用后备特种野母猪32头随机分为8组",玉米-豆粕"型和"40%的稻谷-玉米-豆粕"型日粮各设4个能量水平。结果表明:①养分表观消化率:不同日粮结构对各营养物质表观消化率的影响未达显著水平(P>0.05)。不同能量水平对试验猪只总能、粗蛋白、干物质的表观消化率的影响显著(P<0.05),对粗灰分的表观消化率影响不显著(P>0.05)。②生化指标:不同日粮结构对各生化指标影响均不显著(P>0.05)。不同能量水平对血清TP、血清Alb、血清Glo的影响达到了显著水平(P<0.05)。结论:后备期特种野母猪最适宜的日粮结构为"40%的稻谷-玉米-豆粕"型日粮,消化能为13.00 MJ/kg。     

Effects of dietary energy on control of luteinizing hormone secretion in cattle and sheep.

Prolonged restriction of dietary energy delays onset of puberty, disrupts cyclicity in sexually mature animals, and lengthens the postpartum anestrous period in domestic ruminants. One important mechanism by which energy restriction impairs reproductive activity seems to be suppression of the increase in LH pulse frequency that is necessary for growth of ovarian follicles to the preovulatory stage. Under-nutrition apparently inhibits pulsatile secretion of LH by reducing LHRH secretion by the hypothalamus. The ability of an animal to sustain a high-frequency mode of pulsatile LH release is related to its metabolic status. Mechanisms linking metabolic status to LHRH secretion have not been fully characterized. Changes in body fat have been associated with changes in reproductive activity, but it is unlikely that body fat per se regulates LHRH secretion. It is possible that pulsatile LHRH release is regulated by specific metabolites and(or) metabolic hormones that reflect nutritional status. Alternatively, availability of oxidizable metabolic fuels, such as glucose and nonesterified fatty acids, may influence activity of neurons that control LHRH release. Our understanding of how the central nervous system transduces information about nutritional status into neuroendocrine signals that control reproduction in cattle and sheep is limited by a lack of information concerning the nature of neurons controlling LHRH release in these species.     

Effects of a gonadotropin-releasing hormone antagonist and altrenogest on luteinizing hormone concentration and ovulation in the mare

The objective of Experiment 1 was to determine a dose and frequency of gonadotropin-releasing hormone (GnRH) antagonist administration to effectively suppress serum luteinizing hormone (LH) concentration and to delay ovulation when administered to mares. The objectives of Experiment 2 were 1) to determine the effects of subcutaneous or intravenous administration of a GnRH antagonist or oral altrenogest on serum LH concentration in the estrual mare; and 2) to determine the effectiveness of human chorionic gonadotropin (hCG) in inducing ovulation in mares with suppressed LH concentrations. In Experiment 1, mares (N = 20) were randomly assigned and treated with either 5% mannitol (control, single subcutaneous injection, 1 mL, at time 0; n = 5); low-dose GnRH antagonist (single subcutaneous injection, 0.01 mg/kg, at time 0; n = 5); frequent low-dose GnRH antagonist (subcutaneous injections, 0.01 mg/kg, at 0, 6, 18, and 24 hours; n = 5); or high-dose GnRH antagonist (single subcutaneous injection, 0.04 mg/kg, at time 0; n = 5). Both the frequent low-dose and high-dose GnRH antagonist treatments resulted in significantly lower LH concentrations compared with controls at 90, 102, and 114 hours after treatment (P < .05). In Experiment 2, mares (N = 38) were randomly assigned and treated with subcutaneous sterile saline (control), altrenogest (oral), subcutaneous GnRH antagonist, or intravenous GnRH antagonist. LH concentration for the altrenogest group was lower than the control group at 3, 4, 18, and 30 hours after treatment (P < .05). LH concentration for both the subcutaneous and intravenous GnRH antagonist groups were lower compared with the control group at several time points (P < .05). Based on these data, dose but not frequency of administration of a GnRH antagonist lowered LH concentration in the estrous mare but did not delay ovulation. In addition, serum LH concentrations can be lowered and ovulation effectively postponed in mares treated with altrenogest followed by administration of hCG. This indicates that serum LH concentrations can be lowered and ovulation effectively postponed in mares treated with altrenogest followed by administration of hCG.