The Central Effect of β‐Endorphin and Naloxone on The Biosynthesis of GnRH and GnRH Receptor (GnRHR) in The Hypothalamic‐Pituitary Unit of Follicular‐Phase Ewes

The effects of prolonged, intermittent infusion of β‐endorphin or naloxone into the third cerebral ventricle of follicular‐phase ewes on the expression of genes encoding GnRH and GnRHR in the hypothalamus and GnRHR in the anterior pituitary gland (AP) were examined by an enzyme‐linked immunoabsorbent assay. Activation or blockade of μ‐opioid receptors significantly decreased or increased the GnRH concentration and GnRHR abundance in the hypothalamus, respectively, and affected in the same way GnRHR quantity in the AP gland. The changes in the levels of GnRH and GnRHR after treatment with β‐endorphin as well as following action of naloxone were reflected in fluctuations of plasma LH concentrations. On the basis of these results, it is suggested that β‐endorphinergic system in the hypothalamus of follicular‐phase ewes affects directly or via β‐endorphin‐sensitive interneurons GnRH and GnRHR biosynthesis leading to suppression in secretory activity of the hypothalamic‐pituitary axis.     

Regulation of growth hormone secretion in nursing ewes: an involvement of μ-receptor subtype

Suckling by newborns induces a surge of lactogenic hormones, that is prolactin and growth hormone (GH), in mother's body, with endogenous opioid peptide (EOP) participating in generation of this surge. The aim of the current study was to investigate which types of opioid receptors are involved in generation of the GH surge in ewes during suckling. A series of intracerebroventricular infusions of opioid receptors antagonists: naloxone (for all types of receptors), naloxonazine (specific for μ receptor) and 5'-guanidinonaltrindole (GNTI--specific for κ receptor) and the vehicle (control) were performed in nursing sheep during the fifth week of lactation. All infusions were carried out in a serial manner: five 30-min infusions (60 μg/60 μl) from 10:00 to 15:00, at 30-min intervals. The period of the experiment consisted of the non-suckling (10:00-12:30) and suckling (12:30-15:00) periods. Simultaneously, blood samples were collected at 10-min intervals to determine plasma GH concentration by radioimmunoassay. Suckling evoked a rapid increase in GH concentration in control ewes. Naloxone and naloxonazine significantly decreased both the basal GH release in the non-suckling period and the suckling-induced GH surge. Specifically, the suppressive effect concerned either the duration or the amplitude of the GH surge. In contrast, GNTI did not significantly affect the GH release. In conclusion, the EOPs may affect the regulatory process of GH secretion in lactating sheep, especially through μ opioid receptor.     

Effect of LPS on Reproductive System at the Level of the Pituitary of Anestrous Ewes

In our research we focused our attention on the effect of the immune stress induced by bacterial endotoxin–lipopolysaccharide (LPS) on the hypothalamic–pituitary–gonadal axis (HPG) at the pituitary level. We examined the effect of intravenous (i.v.) LPS injection on luteinizing hormone (LH) and follicle‐stimulating hormone (FSH) release from the anterior pituitary gland (AP) in anestrous ewes. The effect of endotoxin on prolactin and cortisol circulating levels was also determined. We also researched the effect of immune challenge on the previously mentioned pituitary hormones and their receptors genes expression in the AP. Our results demonstrate that i.v. LPS injection decreased the plasma concentration of LH (23%; p < 0.05) and stimulates cortisol (245%; p < 0.05) and prolactin (60%; p < 0.05) release but has no significant effect on the FSH release assayed during 6 h after LPS treatment in comparison with the control levels. The LPS administration affected the genes expression of gonadotropins’β‐subunits, prolactin and their receptors in the AP. Endotoxin injection significantly decreased the LHβ and LH receptor (LHR) gene expression (60%, 64%; p < 0.01 respectively), increased the amount of mRNA encoding FSHβ, FSH receptor (FSHR) (124%, 0.05; 166%, p < 0.01; respectively), prolactin and prolactin receptor (PRLR) (50%, 47%, p < 0.01; respectively). The presented, results suggest that immune stress is a powerful modulator of the HPG axis at the pituitary level. The changes in LH secretion could be an effect of the processes occurring in the hypothalamus. However, the direct effect of immune mediators, prolactin, cortisol and other components of the hypothalamic pituitary–adrenal (HPA) axis on the activity of gonadotropes has to be considered as well. Those molecules could affect LH synthesis directly through a modulation at all stages of LHβ secretion as well as indirectly influencing the GnRHR expression and leading to reduced pituitary responsiveness to GnRH stimulation.     

Central injection of exogenous IL-1β in the control activities of hypothalamic-pituitary-gonadal axis in anestrous ewes

This study was performed to determine the effect of intracerebroventricular (icv) injection of interleukin (IL)-1β on the gene expression, translation and release of gonadotropin-releasing hormone (GnRH) and the GnRH receptor (GnRHR) gene expression in the hypothalamus of anestrous ewes. In the anterior pituitary gland (AP), the expression of genes encoding: GnRHR, β subunits of luteinizing hormone (LH) and folliculotropic hormone (FSH) was determined as well as the effect of IL-1β on pituitary gonadotropins release. The relative mRNA level was determined by real-time PCR, GnRH concentration in the cerebrospinal fluid (CSF) was assayed by ELISA and the plasma concentration of LH and FSH were determined by radioimmunoassay. Our results showed that icv injection of IL-1β (10 or 50 μg/animal) decreased the GnRH mRNA level in the pre-optic area (POA) (35% and 40% respectively; p ≤ 0.01) and median eminence (ME) (75% and 70% respectively; p ≤ 0.01) and GnRHR gene expression in ME (55% and 50% respectively; p ≤ 0.01). A significant decrease in GnRHR mRNA level in the AP in the group treated with the 50 μg (60%; p ≤ 0.01) but not with the 10 μg dose was observed. The centrally administrated IL-1β lowered also GnRH concentration in the CSF (60%; p ≤ 0.01) and reduced the intensity of GnRH translation in the POA (p ≤ 0.01). It was not found any effect of icv IL-1β injection upon the release of LH and FSH. However, the central injection of IL-1β strongly decreased the LHβ mRNA level (41% and 50%; p ≤ 0.01; respectively) and FSHβ mRNA in the case of the 50 μg dose (49%; p ≤ 0.01) in the pituitary of anestrous ewes. These results demonstrate that the central IL-1β is an important modulator of the GnRH biosynthesis and release during immune/inflammatory challenge.     

Does obestatin modulate the hypothalamic appetite‐regulating network in peripubertal sheep?

The participation of peripheral peptides in the processes regulating the food intake (energy homeostasis) at the central nervous system level remains unclear. This study focuses on the role of obestatin in neuronal activity within the hypothalamic appetite‐regulating network in ruminants. The animals (n = 28) were randomly divided into two groups. The sheep in the control group received intracerebroventricular infusions of the Ringer‐Locke solution, and the sheep in obestatin group were infused with obestatin (diluted in the Ringer‐Locke solution) at 25 μg per 120 μl/hr. The series of four 1‐hr infusions on 3 consecutive days were performed, and immediately after the experiment, the sheep were decapitated. Selected brain regions were fixed in situ for further immunohistochemical analysis, while the remaining ones were frozen for real‐time RT‐qPCR analysis. Obestatin infusion elicited changes in the neuropeptide Y (NPY) neuronal network in the hypothalamus. The results obtained show that exogenous obestatin evoked an increase in npy and agrpmRNA expression in the mediobasal hypothalamus (MBH), while the immunoreactivity for NPY was decreased in the arcuate and periventricular nuclei. The increase in cart and pomcmRNA expression in the MBH was also observed. Moreover, increased levels of gpr39 receptor and npy receptor 1 mRNA expression were evident in obestatin‐infused sheep. Based on these results, it can be concluded that obestatin plays a role in the modulation of appetite‐regulating network at the central level in sheep. The results obtained suggest that the underlying mechanism may involve the modification of the activity of NPY/AgRP and CART/α‐MSH neurons in the arcuate nucleus.     

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。     

Expression of Leptin and Long‐form Leptin‐receptor Proteins in Porcine Hypothalamus during Oestrous Cycle and Pregnancy

In this study, we examined the levels of leptin and OB‐Rb protein expression in the discrete areas of the porcine hypothalamus (mediobasal hypothalamus – MBH, pre‐optic area – POA, stalk median eminence – SME) during mid‐ and late‐luteal phases of the oestrous cycle (days 10–12 and 14–16) as well as two stages of pregnancy (days 14–16 and 30–32). The analysis showed that during the cycle, leptin protein expression in MBH was higher in the mid‐luteal phase than late‐luteal phase. In the case of OB‐Rb protein expression, a higher level was observed in MBH during the late‐luteal phase in comparison to the mid‐luteal phase, whereas in POA and SME the opposite dependence was noticed. In turn, during pregnancy, leptin protein expression in MBH and POA, and OB‐Rb protein expression in POA were more pronounced on days 14–16 than on days 30–32. In contrast, leptin protein content in SME as well as OB‐Rb protein in MBH and SME was higher on days 30–32 than during the earlier stage of pregnancy. Comparison of leptin and OB‐Rb protein expression between the cycle (days 10–12) and pregnancy showed a higher level of leptin and OB‐Rb protein contents in POA as well as in SME during pregnancy (on days 14–16 and 30–32, respectively). Yet, OB‐Rb protein expression in POA on days 30–32 of pregnancy was lower in comparison to days 10–12 of the cycle. Furthermore, during pregnancy, leptin protein expression in MBH was lower (days 14–16 and 30–32), whereas OB‐Rb protein expression in that area of hypothalamus was higher (days 30–32) in comparison to the mid‐luteal phase. Our results indicate that both leptin and OB‐Rb are synthesized in the porcine hypothalamus and suggest the participation of leptin in auto/paracrine regulation of these brain areas functions, including control of reproduction during the oestrous cycle and early pregnancy.     

Teladorsagia circumcincta egg output at the onset of natural and induced lactation in ewes

Nineteen ewes maintained under 'worm-free' conditions received anthelmintic and 1 week later were dosed on 5 days each week with 500 Teladorsagia circumcincta larvae for between 10 and 12.5 weeks. Faecal egg counts were determined twice weekly. There were three groups: pregnant (P) ewes (n = 6) which each reared twin lambs, hormone-treated (H) ewes (n = 7) which were not pregnant and were given exogenous hormones (dexamethasone, oestradiol-17 beta, progesterone) for 37 days to induce udder development and milk production, and untreated barren (B) ewes (n = 6). The plasma concentrations of oestradiol-17 beta, prolactin and progesterone were measured. Starting 10-15 days before birth in Group P, there was a biphasic periparturient rise in egg count and the onset of the first peak in egg count preceded the parturient peak in plasma prolactin concentration by several days. Most Group H (5/7) and all Group B ewes remained highly resistant to Teladorsagia infection throughout, despite an induced rise in prolactin concentrations in Group H ewes. It was concluded that factors other than prolactin initiate the periparturient rise but that prolactin is one factor which maintains the response once lactation commences.     

Age-related changes in gonadal and serotonergic axes of broiler breeder roosters

Fertility of domestic roosters decreases at ∼50 wk of age. In a previous study on aging white leghorn roosters, low fertility was accompanied by low levels of both hypothalamic vasoactive intestinal peptide (VIP) and pituitary prolactin (PRL) mRNA expression; however, their role in aging broiler breeder rooster reproduction is still unclear. In this study we compared reproductive activities of young (35-wk-old) and aging (73-wk-old) broiler breeder roosters. Weekly semen volume; concentration and ejaculation grade; and concentrations of plasma testosterone, estradiol, and PRL were examined. Every other week, 10 roosters from each group were euthanized, their testes weighed, and hypothalamus and pituitary removed to determine mRNA expression of hypothalamic GnRH-I, pituitary FSH, pituitary LH, hypothalamic VIP, and pituitary PRL. Aging roosters had significantly lower testis weight and semen volume, sperm concentration, ejaculation grade and plasma testosterone and low hypothalamic GnRH-I, pituitary FSH, and pituitary LH mRNA expression than young roosters (P ≤ 0.05). Aging roosters had higher concentrations of plasma estradiol and PRL and higher hypothalamic VIP and pituitary PRL mRNA expression than young roosters (P ≤ 0.05). We suggest that PRL, which is known to inhibit the gonadal axis, and its releasing factor, VIP, play an important role in the reproductive failure associated with age in broiler breeder roosters.     

Expression of Adiponectin and its Receptors in the Porcine Hypothalamus During the Oestrous Cycle

Adiponectin is a hormonal link between obesity and reproduction, and its actions are mediated by two types of receptors: adiponectin receptor 1 (AdipoR1) and adiponectin receptor 2 (AdipoR2). This study compares the expression levels of adiponectin and adiponectin receptor mRNAs and proteins in selected areas of the porcine hypothalamus responsible for GnRH production and secretion: the mediobasal hypothalamus (MBH), pre‐optic area (POA) and stalk median eminence (SME). The tissue samples were harvested on days 2–3, 10–12, 14–16 and 17–19 of the oestrous cycle. Adiponectin mRNA expression in MBH was significantly lower on days 14–16, whereas in SME, the most pronounced gene expression was found on days 2–3 of the cycle (p < 0.05). Adiponectin protein in MBH was most abundant on days 17–19 and in POA on days 2–3 (p < 0.05). Adiponectin protein expression in SME was at similar level throughout the most of the cycle with a statistically significant drop (p < 0.05) on days 14–16. AdipoR1 gene expression in POA was potentiated on days 2–3 and 10–12 of the oestrous cycle (p < 0.05). In SME, the highest AdipoR1 mRNA expression was noted on days 2–3 (p < 0.05). The concentrations of the AdipoR1 protein in POA were similar throughout the luteal phase (days 2–14 of the cycle), and they decreased on days 17–19 (p < 0.05). In SME, AdipoR1 protein expression peak occurred on days 2–3 (p < 0.05). The expression patterns of the AdipoR2 gene in MBH, POA and SME revealed the highest mRNA levels on days 2–3 of the cycle (p < 0.05). The highest content of AdipoR2 protein in MBH was reported on days 2–3 (p < 0.05), while in POA on days 17–19 and in SME on days 10–12 and 14–16 (p < 0.05). This study demonstrated that adiponectin and adiponectin receptor mRNAs and proteins are present in the porcine hypothalamus and that their expression levels are determined by the pig's endocrine status related to the oestrous cycle.     

Changes in metabolic and reproductive characteristics associated with lactation and glucose infusion in the postpartum ewe

This study examined mechanisms whereby the metabolic environment interacts with basic reproductive function. Ewes lambing during the breeding season were fed to maintain (MAINT, n = 10) or gain (GAIN, n = 11) body weight during the last 4 mo of gestation. From d 7 to 22 postpartum, ewes were infused iv with saline (n = 10) or glucose at a rate calculated to increase normal glucose entry rate by 75% (n = 11). Blood samples were collected daily to determine plasma concentrations of nutritive metabolites and insulin and at frequent intervals on d 14 and 21 to determine serum gonadotropin concentrations. Hypothalami and pituitaries were collected on d 22 to determine hormone content and receptor concentrations. Plasma concentrations of nutritive metabolites and insulin indicated that MAINT ewes mobilized more (P less than .01) body fat and protein reserves during gestation and early lactation than ewes in the GAIN group. Glucose infusion elevated plasma concentrations of glucose (P less than .05) and insulin (P less than .07) and reduced (P less than .05) fat and protein mobilization, even though it depressed feed intake (P less than .001), compared with saline infusion. Hypothalamic gonadotropin-releasing hormone (GnRH), pituitary luteinizing hormone (LH) and follicle-stimulating hormone (FSH) content and pituitary GnRH receptor concentration were similar between treatments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in the gene expression of adiponectin and glucose transporter 12 (GLUT12) in lactating and non-lactating cows

Glucose delivery and uptake by the mammary gland is a rate‐limiting step in milk synthesis. Insulin resistance is believed to increase throughout the body following the onset of lactation. To study glucose metabolism in peak‐, late‐, and non‐lactating cows we analyzed the expression of an adipokine, namely, adiponectin, decreased insulin resistance, leptin, and a novel insulin‐responsive glucose transporter (GLUT12) in the adipose tissue and mammary gland by using real‐time polymerase chain reaction. Our results demonstrated that the mRNA level of adiponectin in the adipose tissue was greater in non‐lactating cows than in peak‐lactating cows. In the adipose tissue, there were no significant differences in the abundance of GLUT12 mRNA between the peak‐, late‐, and non‐lactating cows. In contrast, in the mammary gland, the mRNA level of GLUT12 was greater in non‐lactating cows than in peak‐ and late‐lactating cows. In the adipose tissue, the mRNA level of leptin and peroxisome proliferator‐activated receptor gamma 2 (PPARγ2) was greater in non‐lactating cows than in peak‐lactating cows. The results of the present study suggest that in lactating cows adiponectin plays an important role in insulin resistance in the adipose tissue; in the mammary gland, GLUT12 expression is believed to be an important factor for insulin‐dependent glucose metabolism.     

Digesta kinetics, ruminal fermentation characteristics and serum metabolites of pregnant and lactating ewes fed chopped alfalfa hay

Eight ruminally cannulated ewes (four control and four bred; average BW = 85.7 kg), limit-fed alfalfa hay (1.86% BW), were used in two experiments to determine the effects of pregnancy and lactation on digestive function and serum metabolites. Seven-day sampling periods were used starting on d 102, 118 and 132 of gestation (Exp. 1) and d 14 and 32 of lactation (Exp. 2). Particulate (6.8 vs 4.9%/h; PPR) and fluid passage rates (13.9 vs 10.9%/h) were greater (P less than .05) and gastrointestinal mean retention time (28.9 vs 35.7 h) and fluid turnover time (FTT, 7.5 vs 9.5 h) were lesser (P less than .05) in pregnant than in nonpregnant ewes, respectively. Isobutyrate concentration was lower (P less than .05) in pregnant (1.7 mol/100 mol) than in nonpregnant (1.9 mol/100 mol) ewes. No differences (P greater than .10) were noted for any other ruminal fermentation measures between pregnant and nonpregnant ewes. In Exp. 2, no differences (P greater than .10) were noted in digesta kinetics or ruminal fermentation measures except for isobutyrate and isovalerate molar proportions and serum urea N (SUN) concentration. Isobutyrate, isovalerate and SUN concentrations (21.8 vs 26.1 mg/dl) were lower (P less than .05) in lactating ewes than in nonlactating ewes. Gastrointestinal fill (5.7 vs 7.7 g/kg BW) and FTT (9.3 vs 12.7 h) were lesser and DM digestion (66.7 vs 57.4%) was greater (P less than .05) in lactating than in nonlactating ewes. Data suggest that, during pregnancy, passage rate increases occur without affecting DM digestion and that, during lactation, PPR is not affected when ewes are limit-fed.     

Influence of lactation on the prolactin secreting cells of the hypophysis of impala (Aepyceros melampus): an immunocytochemical and computer image analysis study

Acute stress in the course of wildlife management has been intensively investigated. Chronic stress, on the contrary, has not been researched at all, probably due to the difficulty in measuring it as a result of the overriding effect of the physiological response to the restraining of wild animals. It was therefore decided to evaluate the use of immunocytochemistry, combined with computer image analysis to try and determine the magnitude of the structural changes of various hormone-secreting cells of the hypophysis. Since it was a pilot study to determine whether the combination of immunocytochemistry with computer image analysis could be of value to distinguish between two normally diverse groups, it was decided to compare the relative activity of prolactin secreting cells of lactating and non-lactating impala ewes. After transforming the prolactin immunoreactive area data by log10 to fall inside the parameters for kurtosis and skewness, a significant difference (P < 0.05, 5-% level, 2-tail) with the parametric t-test could be shown between the mean prolactin immunoreactive area of lactating (3.0751 micron 2) and non-lactating (3.0467 micron 2) ewes. However, the Pearson product moment (r = 0.03) showed that this difference may not be important for all practical reasons. This may be due to either sampling errors or limitations of computer image analysis, as it was often difficult to distinguish individual prolactin immunoreactive areas. Furthermore, a significant increase in the total prolactin immunoreactive areas of lactating ewes was also established. This technique, however, could distinguish between the hypophysis of lactating and non-lactating impala ewes, and with further refinement could be a useful tool in determining chronic stress in wildlife populations.     

维生素、矿物质与能量蛋白质水平对浙东白鹅母鹅繁殖性能、血液生殖激素浓度及生殖轴相关基因mRNA相对表达量的影响

本试验通过在饲粮中添加维生素与矿物质、调整饲粮能量蛋白质水平,旨在研究其对浙东白鹅母鹅繁殖性能、血液生殖激素浓度和生殖轴相关基因mRNA相对表达量的影响.选择138只月龄相近的浙东白鹅种母鹅,按体重相近原则分为3组,分别饲喂不同的饲粮,试验期150 d,测定繁殖性能(平均产蛋数、平均蛋重、受精率和孵化率)、血液生殖激素[卵泡刺激素(FSH)、促黄体生成素(LH)、孕酮(P4)、雌二醇(E2)、催乳素(PRL)]浓度和生殖轴相关基因[促性腺激素释放激素(GnRH)、卵泡刺激素-β(FSHβ)、雌激素受体1(ESR1)、雌激素受体2(ESR2)、卵泡刺激素受体(FSHR)、催乳素(PRL)、催乳素受体(PRLR)] mRNA相对表达量的变化.结果表明:1)添加维生素与矿物质可显著提高浙东白鹅母鹅第1产蛋周期平均蛋重和受精率(P＜0.05);提高第2产蛋周期内血液FSH和P4的浓度,降低LH浓度,改变E2、P4和PRL浓度波动(P＜0.05);下调下丘脑PRLR、垂体PRL和卵巢PRLR基因的mRNA相对表达量(P＜0.05),上调卵巢ESR2基因的mRNA相对表达量(P＜0.05).2)调整饲粮能量蛋白质水平可显著提高浙东白鹅母鹅第2产蛋周期平均蛋重(P＜0.05);提高浙东白鹅第2产蛋周期内血液LH浓度,降低FSH浓度,改变E2和P4浓度波动(P＜0.05);上调下丘脑GnRH、垂体PRL和PRLR基因的mRNA相对表达量(P＜0.05),下调卵巢FSHR基因的mRNA相对表达量(P＜0.05).由此得出,添加维生素与矿物质、调整饲粮能量蛋白质水平可通过影响产蛋周期内部分血液生殖激素浓度和波动,局部调节生殖轴相关基因的mRNA相对表达量,改善浙东白鹅母鹅的繁殖性能.     

Influence of glucose infusions on luteinizing hormone secretion in the energy-restricted, primiparous, lactating sow.

The objective of this experiment was to evaluate the influence of glucose infusion during lactation on LH secretion in the energy-restricted sow. Ten primiparous Landrace x Yorkshire sows (152 kg postfarrowing) were fed a low-energy (6.5 Mcal of ME/d), high-lysine (45 g/d), corn-soybean meal diet throughout lactation. On d 18 of lactation, sows received a continuous infusion (1 L/12 h) of glucose (50% dextrose solution) or .9% saline from 1200 to 2400. Blood samples were drawn every 15 min for an 18-h period on d 18 to evaluate concentrations of plasma glucose, serum insulin, and serum LH before (600 to 1200) and during (1215 to 2400) the infusions. The glucose infusion immediately increased (P less than .001) plasma glucose and serum insulin relative to preinfusion levels. Glucose and insulin concentrations in sows receiving the glucose infusion were higher (P less than .001) throughout the infusion period relative to concentrations in sows receiving a saline infusion. Glucose infusions had no influence on LH pulsatility during the 12-h infusion period. In contrast to the response observed in the nutrient-restricted gilt, these results indicate that glucose infusions do not result in an immediate increase in pulsatile LH secretion in the energy-restricted, lactating sow.