Reevaluation of the role of progesterone in stimulating sexual receptivity in estrogen-treated gilts

Three studies were conducted to examine the role of progesterone in stimulating sexual receptivity in estrogen-treated, ovariectomized gilts. Progesterone was administered either before, simultaneously with, or 48 h after estrogen. In each study, gilts were treated with either a suboptimal or an optimal dosage of estradiol benzoate (EB). Progesterone treatment (600 micrograms/kg BW-1 X injection-1) on alternate days for a total of four injections produced serum concentrations of progesterone that were maximal at 9.4 ng/ml and remained greater than 1 ng/ml for 15 d. Estradiol benzoate was administered 22 d after the first of these progesterone injections. When progesterone was administered concurrently with or 48 h after EB, the dosage was 100 micrograms/kg BW and produced a maximal serum progesterone concentration of 1.8 ng/ml 4 h after treatment. Gilts were placed in an evaluation pen with a boar for 5 min on d 3 and 4 after EB treatment. Traits of interest were total number of mounts by the boar, mounts before the gilt showed the immobilization response, proportion of gilts that showed the immobilization response, and latency from entry of the gilt into the evaluation pen until the immobilization response. In none of the three studies did progesterone improve any of the traits of interest. In each study the immobilization response was observed in a higher proportion of gilts treated with the optimal than in those treated with the suboptimal dosage of EB. Latency from entry of gilts into the evaluation pen until the immobilization response was less on d 4 than on d 3 after EB in all studies.(ABSTRACT TRUNCATED AT 250 WORDS)     

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...     

Ovarian influence on uterine growth in prepubertal gilts

A determination of age of the prepubertal gilt at which ovaries affect uterine growth is necessary before establishing the extent to which length of uterus is influenced by inherent differences, as opposed to those due to ovarian secretions. In Exp. 1 and 2, the effect of presence of ovaries on uterine growth was determined following ovariectomy in 186 crossbred gilts. The uterus was examined 40 or 80 d after ovariectomy for length, weight and diameter. Growth of uterine horns in gilts from 20 to 60 d of age was equal with or without ovaries. Uterine horns in ovariectomized gilts continued to grow slowly from 60 to 140 d of age and then remained static to 180 d of age. Uterine horns in gilts with ovaries increased rapidly in length, weight and diameter, with concomitant increase in ovarian weight between 100 and 180 d of age. In Exp. 3, uterine growth and ovarian compensation after unilateral ovariectomy and hysterectomy at 60 d of age were determined in 85 crossbred gilts from 60 to 180 d of age to evaluate the unilateral ovariohysterectomy model for studying association of uterine length before puberty and subsequent uterine capacity. In response to removal of an ovary and a uterine horn, the remaining ovary compensated, but the remaining uterine horn did not. This study demonstrated that the ovaries did not influence uterine growth until after 60 d of age and that unilateral ovariohysterectomy could be performed as early as 60 d of age without altering consequent normal uterine growth.     

Changes in the weight, collagen concentration and content of the uterus and cervix of the ewe during pregnancy

The dry and wet weights of the uterus (caruncular and intercaruncular areas) and cervix were measured in non-pregnant (n = 5) and pregnant (n = 25) ewes post mortem; for the latter, five were obtained for each of the 5 months of gestation. The total collagen tissue content was measured in both areas of the uterus and cervix by hydroxyproline analysis and image analysis of Haematoxylin-Van Gieson stained tissue sections. Both wet and dry uterine weights increased significantly with gestational age (P < 0.001). The water content of uterine and cervical tissue remained constant, at between 83 per cent to 85 per cent and 76 per cent to 80 per cent, respectively. There was a close correlation between the two methods used to determine the collagen content (r = 0.96, P < 0.001), and between the increasing weight of the uterus during pregnancy and the total collagen content of tissues (r = 0.97, P < 0.001). At all stages, the total collagen content of the cervix [mean (SEM) 96.2 (5.4) mg g(-1)] was significantly greater (P < 0.001) than that of the caruncular mean [mean (SEM) 24.3 (1.4) mg g(-1)], and the intercaruncular areas [mean (SEM) 29.0 (1.0) mg g(-1)]. The changes in uterine and cervical weights and collagen content of the tissues were similar to those reported in other related species.     

Changes in weight and composition in various tissues of pregnant gilts and their nutritional implications

The objectives of this study were to characterize the quantitative changes in various body tissues of high-lean type gilts during gestation and to determine the protein needs of pregnant gilts based on changes in tissue contents. Thirty-five gilts (158.2 +/- 8.3 kg) were housed in individual gestation crates with six unbred gilts randomly selected and slaughtered to provide data for d 0 of gestation. The remaining gilts were bred and assigned randomly to one of six slaughter groups: d 45, 60, 75, 90, 102, and 112. Gilts were fed 2 kg (as-fed basis) of gestation diet daily (3.1 Mcal/kg of ME and 0.56% lysine). Carcass soft tissue, bone, gastrointestinal tract, spleen, pancreas, kidney, liver, uterus, fetus, mammary gland, and the remaining viscera were separated and weighed. Carcass soft tissue, liver, remaining viscera, uterus, and gastrointestinal tract were ground, freeze-dried, and analyzed for composition. Body weights of the gilts increased quadratically (P < 0.001) during gestation. Weights of carcass soft tissue and uterus, including placenta, increased linearly (P < 0.001) during gestation. Weights of individual fetuses, fetal litters, individual mammary glands, and the entire mammary glands increased cubically (P < 0.001) during gestation. Crude protein in carcass soft tissue increased cubically (P < 0.01), whereas DM and ether extract (EE) in carcass soft tissue increased linearly (P < 0.01). The DM, CP, and EE in the entire mammary glands increased quadratically (P < 0.001) during gestation. The DM, CP, and EE in fetal litter increased cubically (P < 0.01) as gestation progressed. The accretion rates of the conceptus, fetal litter, individual fetus, individual mammary gland, and CP in fetal litter differed (P < 0.05) before and after d 70 of gestation. The CP daily gain from all maternal and fetal tissues was 40 and 103 g/d before and after d 70 of gestation, respectively, suggesting that pregnant gilts may require different quantities of dietary protein during gestation. Based on the maintenance requirement, maternal tissue gain, and conceptus gain, pregnant gilts require 6.8 and 15.3 g/d of true ileal-digestible lysine (or 147 and 330 g/d of true ileal-digestible protein) before and after d 70 of gestation, respectively, to support their true biological needs.     

Effects of Estradiol and Progesterone on the Numbers and Distribution of Mastocytes in the Uterus of Ovariectomized Rats

The purpose of this study was to investigate the effects of estradiol(E)and progesterone(P)on mastocyte distribution in the uterus of ovariectomized rats.Thirty-five adult female rats were divided randomly into seven groups:one sham operated control group(SHAM);one ovariectomized group(OVX);three ovariectomized plus E treatment groups(OVX+E 20,100,or 500 μg/kg body weight·d);and two ovariectomized plus P groups(OVX+P 2 or 10 mg/kg body weight·d).Seven days after treatment,the contents of estradiol and progesterone in serum were detected by radioimmunoassay,and mastocytes in the uterus were stained by toluidine blue staining.Results were as following:① Compared to ovariectomized rat,the concent ration of estradiol in serum increased by 97.13 % in OVX+E 20(P0.05),204.84 % in OVX+E 100(P0.05),and 936.45 % in OVX + E 500 group(P0.05);the progesterone concent ration increased by 77.25 % in OVX+P 2(P0.05)and 235.25 %in OVX+P 10 group(P0.05).② Compared to ovariectomized rat,the number of mast cells in uteri decreased by 32.65% in OVX+E 20,64.50 % in OVX+E 100(P0.05),74.49 % in OVX+E 500(P0.05)and 70.67 % in OVX+P 10 groups(P0.05).However,the number of mast cells increased by 66.73% in OVX+P 2 group(P0.05)compared with OVX.The trend of mast cells number in the rat uterus was decreased gradually with the increase of estrogen or progesterone concent ration.The number of mast cells in ovariectomized rat uterus was affected by estrogen or progesterone.These results demonstrated that estrogen or progesterone directly affected the number of mast cells in the uterus of rat.     

鹿角盘水提物对大鼠乳腺增生的作用效果及其机制研究

为了探索鹿角盘（DHAB）水提物对大鼠乳腺增生的治疗作用,初步探讨其作用机理和用药剂量,试验利用苯甲酸雌二醇（0.5 mg/（kg·d））联合黄体酮（5.0 mg/（kg·d））对SD大鼠进行肌内注射建立乳腺增生模型。试验共分7个组,每组10只大鼠,分别为空白组、乳腺增生症（HMG）模型组、阳性药三苯氧胺组（0.036 mg/（kg·d））、鹿角盘水提物4个剂量组（高剂量,2.625 g/（kg·d）;中高剂量,1.575 g/（kg·d）;中低剂量,1.05 g/（kg·d）;低剂量,0.63g/（kg·d））。按组别连续灌胃45 d,每周固定时间测定大鼠乳头直径、高度及体重。试验结束后采血取样,称量大鼠胸腺、脾脏、子宫和卵巢质量,取乳腺组织做病理学切片、HE染色,用放射免疫法检测大鼠血清中雌二醇（E₂）及孕酮（P）的含量。结果表明,使用不同剂量鹿角盘水提物均能减小乳腺增生大鼠乳头直径、高度,提高胸腺、脾脏指数,降低子宫指数,减轻乳腺小叶数、腺泡数和分泌物,降低血清E₂含量,升高血清P的含量,与模型组相比有统计学差异（P < 0.01;P < 0.05））。综合试验结果,鹿角盘水提物对乳腺增生大鼠有治疗作用,效果显著,且以中高剂量组变化最为明显。其作用机制可能通过增强机体免疫力、调节血清中E₂、P水平实现。     

The influence of boar pheromones on the vasoreactivity of the facial superficial veins in ovariectomized and estradiol-treated pubertal gilts

This study was designed to establish: a) whether boar pheromones, androstenone and androstenol, may affect the vasocontractility of the facial superficial veins in ovariectomized pubertal gilts and b) what is the effect of estradiol on this contractility. The gilts ovariectomized after two controlled estrous cycles, and the ovariectomized gilts treated with estradiol benzoate were used in the experiment. The isolated rings of dorsal nasal, frontal and facial veins were incubated with androstenone (5alpha-androst-16-en-3-one) and androstenol (5alpha-androst-16-en-3-ol) in concentrations of either 1 or 10 microM. Changes in the contractile activity of the isolated vein segments were measured using isometric transducer and recorded with HSE-ACAD W software. In ovariectomized gilts both the androstenone and androstenol caused a relaxing effect on the nasal vein, flow of the blood from the nasal cavity, and on the frontal vein, by which the blood may by directed into the perihypophyseal vascular complex. An opposing reaction to these pheromones was found in the distal part of the facial vein by which the blood is directed to the systemic circulation. Treating ovariectomized gilts with estradiol benzoate changed mainly the reactivity of the frontal vein to androstenone, which produces constriction, but this treatment did not affect the reactivity of the facial superficial veins to androstenol. The present results demonstrated that both boar sex pheromones, androstenone and androstenol, may contribute to the regulation of their humoral pathway from the nasal cavity to the brain and hypophysis in the ovariectomized pubertal gilts and suggest the effect of estradiol to this pathway.     

Electron microscopic studies of estrogen-induced ciliogenesis and secretion in uterine tube of the gilt.

The time required for occurrence of estrogen-induced uterine tubal (oviductal) ciliogenesis and for differentiation of secretory cells was studied, utilizing electron microscopy procedures. Sixteen cycling gilts were ovariectomized; 3 to 4 months later, 12 principal gilts were each given subcutaneous injections of 17 beta-estradiol in 0.5 ml of corn oil at the rate of 200 mug/day, and 4 control gilts were given injections of corn oil only at the rate of 0.5 ml/day. Two principals each were killed on days 1, 2, 3, 4, 5, and 7 after start of treatment. The epithelial heights were low and completely atrophied 3 to 4 months after ovariectomy. Uterine tubal cilia were absent in all the control gilts. Cytologic changes were not seen in the atrophied epithelium of ovariectomized gilts 1 day after estradiol treatment, but definite proliferative elements consisting of an extensive fibrillar meshwork encrusted with granules (60 to 80 nm) were observed in close association with the nuclear envelope and in the apical cytoplasm after 2 days of estradiol treatment. By day 3, enlarged electron-opaque granules referred to as condensation forms, undergoing various stages of depletion, were closely associated with radially arranged procentrioles. These associations have been referred to as generative complexes. The presence of many generative complexes indicates that maximal production of basal bodies can be expected after 3 days of treatment with estradiol. The depletion of the condensation forms produced hollow spheres with thin walls as the procentrioles grew in length and assembled their microtubules. Enlarged mature-appearing basal bodies were abundant in the cytoplasm after 3 days of estradiol treatment. These bodies aligned themselves linearly along the luminal surface of the cell. Small ciliary buds were then formed above the cell surface, and ciliary filamentogenesis occurred in the bud. Motile cilia were observed on day 3, but cilia numbers increased markedly between day 4 and days 5 and 7. Procentrioles were generated from the diplosomal centriole after 2 days of estradiol treatment. These observations have provided evidence for both ancentriolar and centriolar basal body replication in the ciliated cells of uterine tube of the gilt. Maximal secretory cell differentiation occurred after 3 days of estradiol treatment. Hypertrophy of cytoplasmic organelles was evident on day 3, but the number of secretory granules and amount of rough endoplasmic reticulum increased markedly on days 5 and 7. Close association of secretory granules, Golgi apparatus, and endoplasmic reticulum was evident after estadiol treatment. These data indicate that both ciliated and secretory cells are sensitive to estrogen.     

Countercurrent transfer of 125I-LHRH in the perihypophyseal cavernous sinus-carotid rete vascular complex,demonstrated on isolated pig heads perfused with autologous blood

The objective of the study was to determine whether the local permeability of luteinizing hormone-releasing hormone (LHRH) from the venous blood of the perihypophyseal cavernous sinus into the arterial blood of the carotid rete, supplying the brain and hypophysis in gilts, depends on the day of the estrous cycle, as well as to determine whether this transfer exists when LH concentration in the blood is reduced (the experimental short-loop negative feedback for LH secretion after estradiol injection in ovariectomized gilts). Experiments were conducted on isolated gilt heads with necks, on chosen days of the estrous cycle (n = 40), and on previously ovariectomized gilts treated with estradiol benzoate (EB) (n = 5) or corn oil (n = 3). After exsanguination, the gilt heads with necks were disarticulated and about 30–45 min later were supplied with autologous, oxygenated, and heated blood at a stable blood flow and pressure through the left carotid artery for 30 min. ¹²⁵I-LHRH was infused into both cavernous sinuses through the cannulated angularis oculi veins for 5 min. After ¹²⁵I-LHRH infusion, radiolabeled LHRH was found (P < 0.001) in arterial blood taken from the carotid rete through the open right carotid artery in all animals used in the experiment: on Days 1–2 (six gilts), on Days 12–14 (seven gilts) of the estrous cycle, and in five ovariectomized gilts during negative feedback for LH surge (40 hr after EB). No significant radioactivity of ¹²⁵I-LHRH was found in the arterial blood on Days 3–5 (n = 6), 9–11 (n = 4), and 15–21 (n = 17) of the estrous cycle. A very low level of radioactivity was found in the ovariectomized control group after the injection of corn oil (n = 3). These results provide evidence for the permeability of LHRH from the venous to the arterial blood and its retrograde transport with the arterial blood to the hypophysis and brain, after the ovulation period (Days 1–2) and on Days 12–14 of the estrous cycle. This suggests that a close relationship exists between the day of the estrous cycle and LHRH permeability from the venous to the arterial blood in the perihypophyseal cavernous sinus—the carotid rete complex in gilts—and that this mechanism may be included in a short-loop feedback for LHRH secretion.     

Potential treatments for anestrus in gilts and sows

Pregnant mares' serum gonadotrophin (400 IU) combined with human chorionic gonadotrophin (200 IU) was administered to anestrous gilts (n=31) and sows (n=20) in commercial herds. Two-thirds of the treated animals were mated successfully within seven days and, although no control animals were included, the response indicated that this hormone combination would be useful in herds with anestrous problems. A second experiment was conducted to evaluate the occurrence of estrus and/or ovulations in prepuberal gilts (n=eight/treatment) following injection with pregnant mares' serum gonadotrophin/human chorionic gonadotrophin or other hormones that might stimulate ovarian activity. The pregnant mares' serum gonadotrophin/human chorionic gonadotrophin combination and follicle-stimulating hormone produced estrus within ten days of injection in at least half of the treated gilts but the response was lower with gonadotrophin-releasing hormone and a prostaglandin analogue. Combinations of human chorionic gonadotrophin with small amounts of estradiol benzoate stimulated estrus and ovulation in most of the treated gilts.     

Progesterone increases susceptibility of gilts to uterine infections after intrauterine inoculation with infectious bacteria

In cattle and sheep, a progestogenated uterus is susceptible to infections, but this is not well documented for pigs. Therefore, the effects of day of the estrous cycle and progesterone on the susceptibility to uterine infections were evaluated. Gilts (n = 5 per group) were assigned to treatments in 2 x 2 factorial arrays. In Exp. 1, day of cycle and bacterial challenge were main effects. On d 0 or 8, uteri were inoculated with either 70 x 10(7) cfu of Escherichia coli and 150 x 10(7) cfu of Arcanobacterium pyogenes in PBS or with PBS. In Exp. 2, ovariectomy (OVEX) and progesterone treatment were main effects. On d 0, gilts were ovariectomized or a sham procedure was performed. After surgery, gilts received i.m. injections of progesterone (10 mg/5 mL) or 5 mL of safflower oil diluent twice daily. On d 8, gilts were inoculated with the same doses of bacteria as in Exp. 1. In Exp. 1 and 2, vena caval blood was collected for 4 d, after which uteri were collected. Sediment and ability to culture E. coli and A. pyogenes from uterine flushings were used to diagnose infections. Differential white blood cell counts and lymphocyte response to concanavalin A (Con A) and lipopolysaccharides (LPS) were used to measure lymphocyte proliferation. Progesterone, estradiol-17beta, prostaglandin F2alpha, (PGF2alpha), and prostaglandin E2 (PGE2) were measured in vena caval blood. In Exp. 1, d-8 gilts receiving bacteria developed infections, but d-0 gilts receiving bacteria did not. Daily percentages of neutrophils and lymphocytes changed (P < 0.05) with cycle day and bacterial challenge. Basal- and Con A-stimulated lymphocyte proliferation were greater (P < 0.05) for d-0 than for d-8 gilts. Concentrations of PGF2, (P < 0.01) and PGE2 (P < 0.05) increased after bacterial challenge, regardless of stage of the estrous cycle at the time of inoculation. In Exp. 2, OVEX decreased (P < 0.001) and progesterone treatment increased (P < 0.001) progesterone concentrations, and OVEX decreased (P < 0.01) estradiol-17beta. Gilts with ovarian and/or exogenous progesterone developed infections. Daily percentages of neutrophils and lymphocytes changed in response to OVEX, and neutrophils changed (P < 0.05) in response to endogenous and exogenous progesterone. Lymphocyte proliferation in response to Con A and LPS increased (P < 0.05) with OVEX and decreased (P < 0.05) with progesterone treatment. We conclude that endogenous and exogenous progesterone reduce the ability of the uterus in gilts to resist infections.     

雌性空怀双峰驼生殖道的形态结构

应用组织学方法观察了雌性空怀双峰驼生殖道的形态结构。结果显示，双峰驼生殖道的基本结构与其他哺乳动物相似，但微细结构有差异。双峰驼输卵管粘膜皱襞极其发达，分支多而呈复杂的网状迷路。皱襞基部的迷路酷似固有膜而存在腺体，迷路网格内常见细胞团块。虽然双峰驼怀孕时胎儿位于左侧子宫角，但左、右子宫角以及子宫体的组织结构基本相同。子宫内膜无肉阜，上皮下陷于固有膜内，形成大量长而弯曲的单管状腺。子宫颈固有膜浅层分布有许多小腺体，深层分布有成群的较大腺体。这些腺体为分支管状腺，腺上皮PAS强阳性。阴道粘膜上皮为复层上皮。从输卵管到阴道，粘膜上皮主要为单层柱状上皮，由纤毛细胞和分泌细胞组成，局部可见假复层柱状纤毛上皮。纤毛细胞由前向后逐渐减少，但在子宫颈仍可见到。粘膜上皮和腺上皮内夹有许多淋巴细胞或中性粒细胞，后段局部甚至见到这些免疫细胞浸润于上皮细胞间。固有膜内分布有大量淋巴细胞、中性粒细胞、肥大细胞、浆细胞和巨噬细胞，有时出现淋巴滤泡。     

The effect of spermatozoa and seminal plasma on leukocyte migration into the uterus of gilts.

Yorkshire x Landrace gilts were used to determine the effect of spermatozoa and seminal plasma on postbreeding uterine leukocyte influx. Estrus detection was performed with a boar at 12-h intervals following synchronization with 400 IU eCG and 200 IU of hCG. All gilts were AI once, 24 h after the detection of estrus following random assignment to a 2x2x3 factorial arrangement of treatments (sperm or sperm-free AI doses), AI dose medium (seminal plasma or PBS), and lavage time following AI. Gilts were treated with sperm (5x10(9) spermatozoa; SPZ; n = 30) or sperm-free (SF; n = 30) doses containing either 100 mL of seminal plasma (SP; n = 15/treatment) or PBS (n = 15/treatment). Uterine lavage was performed once on each gilt (n = 20/time) at one of three times after AI (6, 12, or 36 h) to determine the total number of uterine leukocytes. The leukocytes consisted predominately (92 to 99%) of polymorphonuclear neutrophilic granulocytes (PMN). There was an AI x medium interaction on uterine PMN numbers. The number of uterine PMN recovered from gilts inseminated with sperm suspended in PBS was greater than the number of PMN recovered from the uterine lumen of gilts inseminated with sperm in SP, SP alone, or PBS alone (P<.05). Furthermore, SP accelerated the rate of uterine clearance when suspended with sperm cells during the first 36 h following AI (P<.05). These results indicate that seminal plasma suppresses PMN migration into the uterus following breeding and enhances the rate of disappearance of uterine inflammation.     

Effect of recombinant porcine somatotropin on fetal and placental growth in gilts with reduced uterine capacity

Crowded uterine conditions were induced by unilateral hysterectomy-ovariectomy (UHO) in 42 gilts to determine the effect of recombinant porcine somatotropin on fetal and placental growth. Gilts were randomly assigned across three replicates to one of three treatments: Control (C; n = 14), daily injections of 1 mL saline from d 0 to 64 of gestation, Early (E; n = 12), 5 mg of rpST/d from d 0 to 30, followed by 1 mL saline from d 31 to 64, and Late (L; n = 16), 1 mL saline/d from d 0 to 29, followed by 5 mg of rpST/d from d 30 to 64 of gestation. Blood was collected from each gilt via jugular venipuncture at d 0 and every 15 d thereafter. Gilts were hysterectomized on d 65 of gestation. Length of placental attachment and fetal crown-rump length were measured. Placentas and fetuses were weighed. Placental length, wet weight, and dry weight were recorded. Treatment with rpST (either E or L) increased (P < 0.0001) maternal plasma IGF-I concentrations relative to controls. Treatment with rpST did not affect placental wet weight or placental DNA content. However, E and L treatments increased the percentage of placental protein (P = 0.01) and placental dry matter (P = 0.10) and increased contact area of uterine-placental interface (P = 0.01). Despite changes in placental composition and morphology, weights of fetuses collected from L-treated gilts did not differ from controls, whereas weights of fetuses collected from E-treated gilts tended to be less than controls (P < 0.06). Administration of rpST increased maternal IGF-I concentrations and placental surface area but failed to increase fetal growth in the UHO model. Therefore, mechanisms that are independent of maternal IGF-I or placental contact area may control early fetal growth under crowded uterine conditions.     

Growth characteristics, blood metabolites, and insulin-like growth factor system components in maternal tissues of gilts fed L-carnitine through day seventy of gestation

A total of 59 gilts (BW = 137.7 kg) from 3 breeding groups were used to assess the effects of feeding l-carnitine during gestation on gilt growth characteristics, blood metabolites, and uterine and chorioallantoic expression of IGF axis components at d 40, 55, and 70 of gestation. Experimental treatments were arranged in a 2 x 3 factorial, with main effects of added l-carnitine (0 or 50 ppm) and day after initial breeding (d 40, 55, or 70 of gestation). All gilts received a constant feed allowance of 1.75 kg/d and a top-dress containing 0 or 50 ppm of l-carnitine beginning on the first day of breeding through the assigned day of gestation. No dietary treatment differences were observed for gilt BW, backfat, or estimated protein or fat mass at any day of gestation. No differences were observed in circulating total and free carnitine at breeding, but concentrations increased (P < 0.01) as day of gestation increased for gilts fed diets containing l-carnitine compared with those fed the control diet. Maternal IGF-I concentration decreased (P < 0.01) from d 0 to 70 for all gilts, with no differences between treatments. Insulin-like growth factor binding protein-3 mRNA (P = 0.05) and IGFBP-5 mRNA (P = 0.01) increased in the endometrium of gilts supplemented with l-carnitine. These data demonstrate that l-carnitine supplementation and day of gestation alter the expression of the IGF axis by changing the expression of IGFBP at the fetal-maternal interface in swine. These changes in the IGF axis at the fetal maternal interface may aid in determining the reasons for the effects of l-carnitine on reproductive traits.     

Relationship between number of induced ovulations in the prepubertal gilt to the level of progesterone and to the number of spontaneous postpubertal ovulations

A series of experiments were conducted to investigate the relationship between the number of corpora lutea (CL) and concentration of progesterone (P4) on different days after induced and spontaneous ovulation of gilts of different ages. Possible relationship between the number of ovulations after injection of gonadotropin into the prepubertal gilt and the number at a second induced ovulation and finally the number of postpubertal, spontaneous ovulations, was also studied. Number of CL was related (r = .75 to .95, P less than .01) to levels of P4 on d 3 to 10 after induced ovulation of prepubertal gilts of 105 to 180 d of age. Relationship between the number of CL and level of P4 in cyclic gilts ranged from r = .28 to .67 with the highest relationship at d 4 to 9. Number of CL induced at 135 d of age was correlated (r = .67 to .91, P less than .01) with number of CL induced at 195 d. There were correlations (r = .75 to .99, P less than .01) between levels of P4 and number of CL on d 7 to 9 after induction of ovulation of gilts of 135 and 195 d of age with either pregnant mare's serum gonadotropin (PMSG) followed in 96 h by human chorionic gonadotropin (hCG) or estradiol benzoate (EB) followed in 72 h by hCG. There was a correlation (r = .84, P less than .001) between number of CL at the first spontaneous postpubertal estrus and number of CL at third estrus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Elicitation of release of luteinizing hormone by N-methyl-d,l-aspartic acid during three paradigms of suppressed secretion of luteinizing hormone in the female pig.

Two experiments were conducted to determine the minimal effective dose during lactation and site of action of N-methyl-d,l-aspartic acid (NMA) for elicitation of release of luteinizing hormone (LH) in female pigs. In the first experiment, three doses of NMA were given to lactating primiparous sows in which endogenous LH was suppressed by suckling of litters. In the second experiment, ovariectomized gilts were pretreated with estradiol benzoate or porcine antisera against GnRH to suppress LH and then given NMA to determine if it elicited secretion of LH directly at the anterior pituitary or through release of GnRH. In experiment 1, 3 lactating sows (17 +/- 1.5 d postpartum) were each given three doses of NMA (1.5, 3.0 and 5.0 mg/kg body weight [BW]; IV) on 3 consecutive days in a Latin Square design. Blood samples were collected every 10 min from -1 to 1 hr from injection of NMA. NMA at 1.5 and 3.0 mg/kg did not affect (p greater than .5) secretion of LH; however, 5 mg NMA/kg elicited a 114% increase (p less than .001) in circulating levels of LH during 1 hr after treatment. In experiment 2, 8 ovariectomized gilts were given either estradiol benzoate (EB; 10 micrograms/kg BW; IM n = 4) to suppress release of GnRH or porcine antiserum against GnRH (GnRH-Ab; titer 1:8,000; 1 ml/kg BW; IV; n = 4) to neutralize endogenous GnRH. Gilts infused with GnRH-Ab were given a second dose of antiserum 24 hr after the first. Gilts were then given NMA (10 mg/kg BW; IV) 33 hr after EB or initial GnRH-Ab. Blood samples were drawn every 6 hr from -12 to 24 hr from EB or GnRH-Ab treatments, and every 10 min from -2 to 2 hr from NMA. Serum LH declined (p less than .001) after EB (from 1.87 +/- .2 ng/ml at 12 hr before EB to 0.46 +/- .02 ng/ml during 24 hr after EB) and GnRH-Ab (from 1.97 +/- .1 to 0.59 +/- .02 ng/ml). In gilts treated with EB, the area under the curve (AUC) for the LH response (ng.ml-1.min) 1 hr after NMA (38.7 +/- 3) was significantly greater (p less than .01) than the 1 hr prior to NMA (21.3 +/- 1.5). Treatment with NMA had no effect (p greater than .5) on secretion of LH in gilts infused with GnRH-Ab.(ABSTRACT TRUNCATED AT 400 WORDS)     

日粮不同营养水平对母猪妊娠早期胚胎存活的影响

试验以63头长白-大白杂交初产母猪为试验动物,研究不同营养水平对母猪妊娠早期繁殖性能的影响。将配种后母猪随机分到3个营养水平组(高、中、低)中,各营养水平通过每天供给2、1.2和0.6倍维持需要的饲粮,分别在妊娠12、25和35d将母猪称重、屠宰。结果表明:各水平组母猪妊娠12、25和35d的母体总增重和净增重有极显著(P<0.01)差异。中水平妊娠25d的子宫及内容物重量和两侧子宫角长度均显著(P<0.05)高于高水平和低水平;中水平妊娠35d的子宫及内容物重量和右侧子宫角长度显著(P<0.05)高于高水平。中水平妊娠12 d的总活胚数显著(P<0.05)高于高水平。中水平妊娠12、25和35d的胚胎存活率显(著P<0.05)高于高水平;中水平妊娠25d和35d的胚胎存活率显著(P<0.05)高于低水平。中水平妊娠35 d的活胚重显著(P<0.05)高于高水平,极显著(P<0.01)高于低水平。以上试验表明,在妊娠35d内给母猪饲喂1.2倍维持需要能使子宫发育更良好,并具有较高的胚胎存活率,而高水平饲喂和严重限饲均会导致母猪妊娠早期的胚胎存活率降低。