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1.
Maternal nutrient restriction from early to midgestation can lead to fetal growth retardation, with long-term impacts on offspring growth, physiology, and metabolism. We hypothesized that ewes from flocks managed under markedly different environmental conditions and levels of nutrition might differ in their ability to protect their own fetus from a bout of maternal nutrient restriction. We utilized multiparous ewes of similar breeding, age, and parity from 2 flocks managed as 1) ewes adapted to a nomadic existence and year-long, limited nutrition near Baggs, WY (Baggs ewes), and 2) University of Wyoming ewes with a sedentary lifestyle and continuous provision of more than adequate nutrition (UW ewes). Groups of Baggs ewes and UW ewes were fed 50 (nutrient restricted) or 100% (control fed) of National Research Council recommendations from d 28 to 78 of gestation, then necropsied, and fetal and placental data were obtained. Although there was a marked decrease (P < 0.05) in fetal weight and blood glucose concentrations in nutrient-restricted vs. control fed UW ewes, there was no difference in these fetal measurements between nutrient-restricted and control-fed Baggs ewes. Nutrient-restricted and control-fed UW ewes exhibited predominantly type A placentomes on d 78, but there were fewer (P c0.05) type A and greater (P < 0.05) numbers of type B, C, and D placentomes in nutrient-restricted than control-fed Baggs ewes. Placental efficiency (fetal weight/placentomal weight) was reduced (P = 0.04) in d 78 nutrient-restricted UW ewes when compared with control-fed UW ewes. In contrast, nutrient-restricted and control-fed Baggs ewes exhibited similar placental efficiencies on d 78. This is the first report of different placental responses to a nutritional challenge during pregnancy when ewes were selected under different management systems. These data are consistent with the concept that Baggs ewes or their conceptuses, which were adapted to both harsh environments and limited nutrition, initiated conversion of type A placentomes to other placentomal types when subjected to an early to mid-gestational nutrient restriction, whereas this conversion failed to occur in UW ewes. This early placentomal conversion in the Baggs ewes may function to maintain normal nutrient delivery to their developing fetuses during maternal nutrient restriction.  相似文献   

2.
An approach was developed for describing live weight gain and the contribution of wet gut fill gain to live weight gain in growing cattle. In a continuous growth study, energy densities of winter:spring diets were used to define four treatment groups of cattle. Concentrates and forages were the major ingredients of higher and lower energy-density diets, respectively. Cattle receiving high and low energy sequences (HH and LL) were designated as control groups and were compared with two change-over groups: high to low (HL) and low to high (LH). Switches involved simultaneous changes in several feed characteristics. Every 2 wk for 4 mo, 39 heifers and 19 steers were weighed. Switching young cattle to another diet affected growth during the 2 wk immediately after the switch. After being switched to the lower energy-density diet (i.e., pasture), HL and LL groups lost (P less than .001) from 3.5 to 27.4 kg in both fed and fasted weight. Neither fed nor fasted weights of HH and LH steers changed during the switch to the higher energy-density diet (i.e., concentrates); HH and LH heifers continued to gain (P less than .001). Throughout the remainder of the study, growth rates of cattle were similar for HH and LH groups and for HL and LL groups. In spring, cattle consuming concentrate diets (HH and LH) had greater fill (P less than .001) than pasture-fed contemporaries (HL and LL). Less frequent measurement of growth characteristics would have obscured important facets of growth. A loss of weight followed by continuous gain is not equivalent to a reduced growth rate.  相似文献   

3.
本研究通过对新疆某肉牛养殖场架子牛育肥经济效益的调研分析,旨在为新疆肉牛养殖从业者选择架子牛育肥模式提供理论参考。购入高、低初始重的新疆褐牛与本地土牛杂交架子牛各24头,分为高成本高初始重组(HH组)、低成本高初始重组(LH组)、高成本低初始重组(HL组)、低成本低初始重组(LL组),每组12头牛,育肥周期为7-9个月,每月称重并记录结果,并对数据进行分析。单因素方差分析结果显示,LL组末重极显著低于其它3组(P<0.01),HH组末重显著高于LH组和HL组(P＜0.05);育肥期平均日增重LL组显著低于其它3组(P＜0.05),HH组、LH组和HL组虽然差异不显著(P>0.05),但是HH组和HL组日增重大于LH组。经济效益分析结果显示,成本利润率HL组>HH组>LL组>LH组。相关性分析结果显示,成本利润率与平均日增重呈极显著正相关关系(P<0.01),与日饲喂成本呈现显著正相关关系(P<0.05)。本研究发现,在架子牛育肥过程中,高饲喂成本投入可以获得更高的经济效益,选择低初始重的架子牛进行短期高营养水平育肥,比选择高初始重的架子牛育肥经济效益更好。  相似文献   

4.
本试验旨在研究妊娠后期限饲蒙古绵羊对其胎盘生长发育及胎盘块类型分布的影响。选择健康蒙古绵羊42只(经同期发情且受孕),于妊娠90 d选择6只母羊进行屠宰,其余按体重随机分配到3个组:0.175 MJ/(kgW0.75.d)(RG1:n=14)、0.33 MJ/(kgW0.75.d)(RG2:n=12)和自由采食组0.67 MJ/(kgW0.75.d)(CG:n=10),进行不同能量水平饲养至妊娠140 d,再选择6只母羊进行屠宰。结果表明:妊娠后期限饲母羊严重影响了RG1组(P<0.01)、RG2组(P<0.05)的胎盘重及胎儿重(P<0.01);RG1组A类型胎盘块重量(P<0.01)、数量(P<0.01)与RG2组A类型胎盘块数量(P<0.05)显著低于CG组;RG1组B类型胎盘块重量(P<0.05)、数量(P<0.01)与RG2组B类型胎盘块数量(P<0.05)显著高于CG组;随着母体营养水平的降低,C、D类型胎盘块出现的几率增加,且C、D类型胎盘块血管数量显著高于A、B类型胎盘块血管数量(P<0.05)。这说明妊娠后期限饲蒙古绵羊影响了胎盘的生长发育,使得胎盘块数量、重量、类型和血管数量等发生了明显改变。  相似文献   

5.
To evaluate the effects of pre- and post-conception undernutrition (UN) on fetal and placental development at mid-gestation, 28 Katahdin × Pelibuey multiparous ewes were blocked by weight and assigned to the following four dietary treatments (n = 7 each): ewes fed 100% (control) or 60% of their nutritional requirements 30 days before mating (UNPre), 50 days after mating (UNPost) or during both periods (UNB). Four twin-bearing ewes were selected per treatment at day 50 post-conception and then slaughtered at day 75 of gestation to analyze their fetuses. Control fetuses were heavier (P < 0.05) than UNPost and UNB fetuses in 14.6 and 9.4%, respectively. Organ weights as percentage of the fetal weight (except for liver) and morphometric measurements (except for abdominal girth) were similar between control and UN fetuses (UNPre, UNPost, and UNB). Placental mass was heavier (P < 0.05) in control ewes than UNB ewes, but not relative to ewes of other treatments. The number of placentomes per ewe and placental efficiency were unaffected by UN treatments. Compared to control, only UNB ewes exhibited variations (P < 0.05) in the proportion of placentomes, specifically for type A (+13.8%) and B (?12.6%). Placentomes of type A and B had lower weight, length, and width of placentas in UNPost and UNB ewes than placentas of control ewes (P < 0.05). Overall results indicate that fetal and placental development of ewes carrying twins is mainly altered when nutritional restriction occurs simultaneously before conception and during the first third of pregnancy.  相似文献   

6.
本试验旨在研究牛至油(Oo)和过瘤胃蛋氨酸(RPMet)的不同添加量组合对奶牛产奶性能与氮排泄的影响。选取年龄、体重、胎次、产奶量、乳成分及泌乳期(90±15) d相近的荷斯坦奶牛40头随机分为10个组,每组4头。对照(C)组饲喂基础日粮,试验组饲喂不同添加水平的Oo和RPMet,Oo添加水平分别为11.5(L)、13.0(M)、14.5(H) g·(d·头)-1;RPMet添加水平分别为22.5(L)、25.0(M)、27.5(H) g·(d·头)-1,共组成9个不同的添加量组合,分别为LL、ML、HL、LM、MM、HM、LH、MH、HH(第1个字母为Oo添加水平,第2个字母为RPMet添加水平)。预试期15 d,正试期60 d。结果表明:产奶量方面,LL、HL、HM、MH、HH组产奶量极显著高于对照组(P<0.01),以MH组最高。乳成分方面,MH、HM组乳脂率极显著提高(P<0.01);HM、HH组乳蛋白率极显著提高(P<0.01),各试验组在乳体细胞数均极显著低于对照组(P<0.01)。在氮排泄方面,LL、ML、LM、MM、HM、LH、MH、HH组氮排泄极显著低于对照组(P<0.01),以MH组最低。综合考虑上述指标,在本试验条件下,以MH组[Oo 13.0 g·(d·头)-1、RPMet 27.5 g·(d·头)-1]组合效果最好。  相似文献   

7.
本试验旨在探讨饲粮蛋白质和脂肪水平对育成期雌性水貂生长性能、营养物质消化率及氮代谢的影响,以确定育成期雌性水貂饲粮中蛋白质和脂肪的适宜水平。采用2×3因子试验设计,设32%(L)、36%(H)2个蛋白质水平与10%(L)、20%(M)、30%(H)3个脂肪水平,共配制6种试验饲粮。按照蛋白质和脂肪水平,将6种试验饲粮分别命名为LL、LM、LH、HL、HM和HH。选取90只60日龄健康雌性水貂,随机分成6组,每组15个重复,每个重复1只水貂。预试期7 d,正试期60 d。结果表明:LH组水貂末重和平均日增重均最高,显著高于LL和HL组(P0.05),并且随着饲粮脂肪水平的增加呈上升趋势。平均日采食量和料重比均以LH组最低;30%脂肪水平组水貂的平均日采食量极显著低于20%脂肪水平组(P0.01);料重比随着饲粮脂肪水平的增加而升高,30%脂肪水平组极显著低于10%和20%脂肪水平组(P0.01)。LL和HL组水貂的干物质消化率、脂肪消化率极显著低于其他组(P0.01);HH组水貂的蛋白质消化率显著高于LL、LH和HL组(P0.05)。随着饲粮蛋白质水平的增加,蛋白质消化率和脂肪消化率分别显著(P0.05)和极显著(P0.01)升高;10%脂肪水平组的干物质消化率和蛋白质消化率极显著低于20%和30%脂肪水平组(P0.01);随着饲粮脂肪水平的增加,脂肪消化率呈升高趋势;碳水化合物消化率则以30%脂肪水平组最低,极显著低于10%和20%脂肪水平组(P0.01)。水貂食入氮以HM组最高,极显著高于其他各组(P0.01);粪氮排出量以HL组最高,显著高于LH和HH组(P0.05);尿氮排出量以LH组最低,而氮沉积和氮生物学效价则以LH组最高。随着饲粮蛋白质水平由32%增加到36%,食入氮和尿氮排出量极显著增加(P0.01),而氮生物学效价则显著降低(P0.05)。20%脂肪水平组食入氮最高,极显著高于30%脂肪水平组(P0.01);粪氮排出量和尿氮排出量均以30%脂肪水平组最低,与10%和20%脂肪水平组存在显著(P0.05)或极显著(P0.01)差异;随着饲粮脂肪水平的增加,氮沉积呈先升高后降低的趋势,而氮生物学效价呈升高的趋势。综合各项指标,在本试验条件下,当饲粮蛋白质水平为32%、脂肪水平为20%~30%时,育成期雌性水貂生长性能最佳,且能够降低尿氮排出量,提高水貂对饲粮蛋白质的利用率。  相似文献   

8.
The amount of messenger RNA (mRNA) for luteinizing hormone beta-subunit (LH beta), follicle-stimulating hormone beta-subunit (FSH beta) and alpha-subunit was measured during estradiol-17 beta (E) positive feedback in ovariectomized (OVX) ewes. During the anestrous season, OVX ewes were given an i.m. injection of E (25 micrograms: n = 5) or oil (control; n = 4) and hourly blood samples were collected for 16 hr. After blood collection, ewes were killed and anterior pituitary glands were removed for analysis of hormone and mRNA content. Preovulatory-like increases in serum concentrations of LH and FSH were measured in E-treated OVX ewes. In two E-treated OVX ewes the serum concentrations of LH and FSH were still increasing, whereas in the remaining three E-treated OVX ewes, serum concentrations of LH were on the decreasing portion of the E-induced preovulatory-like surge. Pituitary content of LH was lower (P less than .10) in E-treated OVX ewes when serum concentrations of LH were decreasing than that measured in control ewes or E-treated OVX ewes in which serum concentrations were still increasing. Pituitary content of FSH and prolactin were similar (P greater than .05) among all groups. The amount of mRNA for LH beta-subunit was similar (P greater than .05) in ewes in which serum concentrations of LH were increasing and in control ewes, but was lower (P less than .05) in ewes with decreasing levels of LH. The amount of mRNA for FSH beta-subunit was lower (P less than .05) in all E-treated OVX ewes (independent of whether serum concentrations of FSH were increasing or decreasing) than that measured in control ewes. There was no difference (P greater than .05) in the amount of mRNA for alpha-subunit among any groups. Thus, amounts of mRNA for the beta-subunits of gonadotropins are reduced, while amounts of mRNA for alpha-subunit are unchanged during estradiol positive feedback in OVX ewes.  相似文献   

9.
本试验旨在研究过瘤胃蛋氨酸(RPMet)和肉桂醛(CA)组合添加对奶牛产奶性能及氮排泄的影响。选取年龄、体重、胎次、产奶量、乳成分及泌乳期[(90±15)d]相近的荷斯坦奶牛40头分为10组,每组4头。对照(C)组饲喂基础饲粮,试验组补饲不同水平的RPMet和CA,其中RPMet设3个水平,分别为20(L)、25(M)、30(H)g/(d·头);CA设3个水平,分别为15(L)、18(M)、21(H)g/(d·头),共组成9个不同水平组合,分别为LL、ML、HL、LM、MM、HM、LH、MH、HH(第1个字母为RPMet添加水平,第2个字母为CA添加水平)。预试期15d,正试期60d。结果表明:1)除LH组外,各试验组产奶量均显著或极显著高于C组(P0.05或P0.01),以HL组最高。2)各试验组乳脂率和乳蛋白率均高于C组,均以HL组最高,与C组均差异极显著(P0.01);各试验组乳体细胞数均低于C组,以HL组最低,与C组均差异极显著(P0.01)。3)除LH组外,各试验组氮表观消化率和氮泌乳转化效率均显著或极显著高于C组(P0.05或P0.01),以HL组最高;LL、ML、HL、LM、MM、HM、LH、MH、HH组总氮排泄量比C组分别降低了17.45%(P0.01)、18.79%(P0.01)、20.80%(P0.01)、10.41%(P0.01)、12.49%(P0.01)、15.22%(P0.01)、3.37%(P0.05)、5.12%(P0.05)、7.43%(P0.05),以HL组最低。结果提示,在泌乳奶牛饲粮中联合添加RPMet和CA可以提高奶牛产奶性能、降低奶牛氮排泄量;综合考虑上述指标,最佳组合为RPMet 30g/(d·头)、CA 15g/(d·头)。  相似文献   

10.
Aspects of placental protein and energy metabolism were examined in pregnant ewes subjected to either thermoneutral (TN, 18 to 20 degrees C, 30% humidity, n = 7) or hot (H, 30 to 40 degrees C, 40% humidity, n = 5) temperatures through mid and late gestation. Fetal and placental weights and total content of protein, RNA, and DNA were reduced (P less than .001) in H ewes. Placental protein and RNA concentrations (mg/g) were not different, and DNA concentrations were slightly greater (P less than .1), in H vs TN ewes. Thus, heat seemed to greatly reduce total cell number and placentome size and only slightly decrease cell size. Ratios of RNA to DNA indicated a reduced capacity for protein synthesis in H placenta. However, in vitro fractional rates of protein synthesis in tissue slices from the fetal and maternal placenta and from the myoendometrium were not different between TN and H ewes. The H ewes had greater placental protein concentrations of hydroxyproline and glycine, perhaps suggesting a greater collagen content. In vitro oxygen consumption of fetal placenta, but not of maternal placenta or myoendometrium, was lower in H than in TN ewes. This lower oxygen consumption was partially due to a lower Na+,K+ ATPase-dependent oxygen consumption.  相似文献   

11.
In this study we evaluated maternofetal transmission of immunoglobulins in ewes under conditions of altered placental morphology. Intravenous injection of human red blood cells was used to induce immunoglobulins in pregnant ewes. The hemagglutination test was used to detect antibody in maternal serum, fetal and placental fluids. Placental injury was induced by intravenous inoculation of Escherichia coli endotoxin or spores of Aspergillus fumigatus into pregnant ewes at days 99 or 100 of gestation respectively. Placental infarction, thrombosis of maternal placental vessels and variable neutrophil infiltrate characterized lesions produced by A. fumigatus. Endotoxin treated ewes developed marked placental edema, congestion, hemorrhage and focal loss of uterine epithelium. Human red blood cell agglutinating antibody was not detected in placental or fetal fluids obtained from ewes with either of the above placental lesions. Placentitis of undetermined etiology was observed in seven ewes. Two ewes had received A. fumigatus, two had received endotoxin and three were untreated ewes. Histological examination of their placentas revealed trophoblastic and endometrial epithelial necrosis and necrotizing vasculitis of the chorioallantois. Human red blood cell agglutinating antibody was detected only in the fetal and placental fluids of the seven ewes with these placental lesions. The nature of these lesions would have produced a functional confluence of the maternal and fetal circulations. Antibody transfer from dam to fetus was observed only in association with placental lesions which produced this confluence of circulations. The character of the placental lesions, rather than the mere presence of placental lesions apparently determined the transfer of immunoglobulins.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

12.
The concentration of ovine placental lactogen (oPL) in maternal plasma varies with litter size and nutritional status, making it difficult to compare these concentrations across studies. In this study, 27 Dorset and Finn-Dorset crossbred ewes with litters of known size and gestational age were used to relate concentrations of oPL in maternal plasma to placental and fetal weights. Fetal oPL concentrations also were correlated to these variables in 12 chronically catheterized singleton fetuses. The concentration of oPL in maternal plasma increased with increasing placental weight across litter sizes ranging from 1 to 3 (r = .716). When expressed per gram of placenta, oPL was greater (P less than .05) in those ewes carrying multiple fetuses. There was no correlation between maternal and fetal oPL in time-matched samples or in average values between individuals for ewes carrying singleton pregnancies. Within the singleton group, placental weight and fetal weight were well correlated (r = .761), as were the concentration of fetal plasma oPL and fetal weight (r = .699). Placental weight plus fetal oPL could explain 81% of the variation seen in fetal weight. These results imply that maternal and fetal oPL release are controlled independently and that fetal oPL affects fetal growth by a mechanism not directly related to placental size.  相似文献   

13.
Forty crossbred wethers (BW = 28.7 kg) were used to evaluate the effects on LM lipid composition of diets containing high and low levels of vitamin A. Four treatments arranged as a 2 x 2 factorial with a completely random design were investigated: backgrounding (BG) and finishing (FN) with no supplemental vitamin A (LL); BG with no supplemental vitamin A and FN with high vitamin A (6,600 IU/kg of diet, as fed) supplementation (LH); BG with high vitamin A supplementation and FN with no vitamin A supplementation (HL); and BG and FN with high vitamin A (HH) supplementation. Diets included cracked corn (62.4%), soybean meal (16.0%), cottonseed hull pellets (14.8%), and supplement (7%), and contained <100 IU of vitamin A/kg (as fed) from carotenes before vitamin A was added. During the BG period (d 1 to 56), feed intake was restricted to achieve 0.22 kg of ADG. During the FN period (d 57 to 112), lambs consumed the same diet ad libitum. Lambs were weighed every 14 d, and blood was sampled every 28 d to evaluate changes in serum fatty acids and vitamin A levels. Lambs were slaughtered after 112 d. Lipid composition was determined for liver and LM. There were no treatment differences (P > 0.05) in feed intake, ADG, or final BW. Carcass weights were not affected by vitamin A treatment (P > 0.20), although backfat thickness tended to be different between HL and LL lambs (0.80 vs. 0.64 cm, respectively; P = 0.08). Carcasses from the HH group had greater (P < 0.05) marbling scores than those from the LL group (514 vs. 459) and had 25.8% more extractable intramuscular lipids (3.88 vs. 3.08% for HH and LL, respectively; P < 0.05); the LH and HL treatments were intermediate. Interestingly, the LL group had the greatest increase in serum fatty acids throughout the experimental period (change of 127 vs. 41 microg/g for LL and HH, respectively; P < 0.01). The degree of saturation of fatty acids was not affected by treatment (P = 0.18) in the serum but was affected in the longissimus thoracis fat. Oleic acid increased and linoleic acid decreased in the longissimus thoracis of HH-treated lambs (P < 0.02). These data suggest that increases in total intramuscular lipids may be achieved with high levels of vitamin A supplementation for 112 d in young lambs.  相似文献   

14.
本试验旨在研究牛至油(Oo)与过瘤胃蛋氨酸(RPMet)的不同添加组合对奶牛瘤胃微生物蛋白(MCP)产量与养分消化率的影响。选取年龄、体重、胎次、产奶量、乳成分及泌乳期(90±15)d的荷斯坦奶牛40头,分为10个组,每组4头。对照(C)组饲喂基础日粮,试验组饲喂不同添加水平的Oo和RPMet,Oo设置3个梯度,添加量分别为11.5(L)、13(M)、14.5(H)g/(d·头);RPMet设置3个梯度,添加量分别为22.5(L)、25(M)、27.5(H)g/(d·头),共组成9个不同的添加量组合,分别为LL、ML、HL、LM、MM、HM、LH、MH、HH(第1个字母为Oo添加水平,第2个字母为RPMet添加水平)。预试期15 d,正试期60 d。结果表明:各试验组奶牛的微生物蛋白(MCP)产量均有提高,其中MH、ML、LH、LM、HM组的MCP产量显著提高;试验组奶牛的养分表观消化率有提高趋势,其中MH、HM组粗蛋白质消化率极显著提高;HH、MH组中性洗涤纤维消化率显著提高,酸性洗涤纤维消化率极显著提高;MH组干物质消化率显著提高。在本试验条件下,综合考虑瘤胃MCP产量以及各主要养分的表观消化率,以Oo 13 g/(d·头)、RPMet 27.5 g/(d·头)组合(MH组)效果最好。  相似文献   

15.
This study was designed to evaluate profiles of serum concentrations of LH, pituitary content of LH and GnRH receptors, and hypothalamic content of GnRH in undernourished, ovariectomized ewes. In earlier studies, pulsatile secretion of LH diminished as duration of undernutrition progressed in prepubertal or adult ovariectomized ewes. Ewes having similar body condition scores (CS) of 5 to 9 (1 = extremely thin, 5 = moderate, 9 = obese) were fed maintenance or low-energy diets (100% and 60% of NRC requirements, respectively). Blood samples for analysis of LH were collected at 15-min intervals for 4 h at initiation of the project and immediately prior to slaughter. Serum concentrations of LH did not differ (P greater than .05) among groups at the initial sampling period. At slaughter, ewes with CS less than or equal to 2 (n = 7) had lost 26.8 kg (42% of initial weight). Ewes with CS greater than or equal to 3 (n = 12) had lost an average of 13.7 kg (18% of initial weight). Concentrations of LH in ewes with final CS greater than or equal to 3 was similar (P greater than .05) to that observed during the initial sampling period. However, release of LH was reduced (P less than .01) in ewes with CS less than or equal to 2 compared with ewes with CS greater than or equal to 3 (2.6 vs 9.5 and 3.2 vs 10.5 ng/ml for basal and mean concentrations, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

16.
Pregnant ewes were chronically exposed to thermoneutral (TN; 20 degrees C, 30% relative humidity) or hot (H; 40 degrees C 9 h/d, 30 degrees C 15 h/d, 40% relative humidity) environments between d 64 and 136 to 141 of pregnancy. They were sampled for blood at 14-d intervals during this period for measurement of plasma metabolites and hormones, then slaughtered and dissected to measure conceptus weights, dimensions and fetal organ weights. Rectal temperatures of H ewes were elevated .3 to 1.0 C degrees above those of TN ewes throughout the experiment. Voluntary feed intakes were not altered by heat exposure except after 120 d of pregnancy, when feed intake was about 25% lower (P less than .10) by H than by TN ewes. Blood 3-hydroxybutyrate concentrations were not affected by heat, but plasma glucose concentrations were greater in H than in TN animals after 120 d (P less than .05). Placental weight, reduced by 54% (P less than .001) by heat exposure of ewes, was correlated positively with fetal weight and correlated negatively with fetal/placental weight ratio, fetal brain/liver weight ratio and fetal relative heart weight. Late in pregnancy, plasma concentrations of progesterone, cortisol and placental lactogen were reduced (P less than .01) in H ewes, whereas triiodothyronine levels were markedly lower (P less than .03) at all stages of pregnancy. Plasma concentrations of prolactin were elevated dramatically (P less than .01) and a modest increase (P less than .03) in somatotropin levels was recorded in H ewes. These results are consistent with our hypothesis that heat-induced fetal growth retardation is secondary to a primary reduction in placental growth; this could be mediated partly by reduced peripheral activity of thyroid hormones. Heat-induced reductions in secretion of progesterone and ovine placental lactogen more likely were a consequence than a cause of placental stunting.  相似文献   

17.
本试验旨在研究牛至油(Oo)与肉桂醛(CA)的不同添加组合对奶牛瘤胃微生物蛋白产量与养分消化率的影响。选取年龄、体重、胎次、产奶量、乳成分相近及泌乳期为(90±15)d的荷斯坦奶牛40头,随机分为10个组,每组4头。对照组(C)饲喂基础日粮,试验组饲喂不同添加水平的Oo和CA,Oo 3个梯度分别为11.5(L)、13(M)、14.5(H)g/(d·头);CA 3个梯度分别为15(L)、18(M)、21(H)g/(d·头),共组成9个不同的添加量组合,分别为LL、ML、HL、LM、MM、HM、LH、MH、HH(第1个字母为Oo添加水平,第2个字母为CA添加水平)。预试期15 d,正试期60 d。结果表明:试验组奶牛的瘤胃微生物蛋白(MCP)产量均有提高趋势,其中LH组效果最好,瘤胃MCP产量比C组提高了12.82%(P<0.05);试验组奶牛在养分表观消化率方面有提高趋势,其中以LH组最优,干物质与粗蛋白质的消化率高于C组(P<0.05),中性洗涤纤维与酸性洗涤纤维的消化率高于C组(P<0.01)。本试验条件下,综合考虑瘤胃MCP产量以及各主要养分的表观消化率,以添加Oo 11.5 g/(d·头)、CA 21 g/(d·头)为最佳。  相似文献   

18.
The objective of this study was to identify rams exhibiting high (HP) and low (LP) levels of sexual performance and to determine whether their respective behavioral responses to ewes in estrus were related to changes in serum testosterone (T) and LH concentrations. Rams were selected on the basis of standardized serving capacity tests. Plasma T and LH concentrations in rams were measured in three experiments: 1) after 15 min of exposure to estrous ewes, 2) after an injection of 500 ng of LHRH, and 3) during an 11-h exposure to estrous ewes. During 15 min of exposure to ewes, HP rams were sexually active, whereas LP rams showed no sexual interest. Secretion of LH was similar (P greater than .05) between ram groups. Sexual arousal, copulation, and ejaculation of HP males were not related (P greater than .05) to LH secretion. Exposure to estrous ewes for 11 h, however, stimulated LH pulse frequency and elevated basal LH and T concentrations in HP but not LP rams (P less than .001). Luteinizing hormone secretion was positively correlated to the frequency of mounts (r = .19; P less than .01) and ejaculation (r = .17; P less than .03). Aggressive behavior of rams directed at ewes was negatively correlated to LH (r = -.22 P less than .003). Concentrations of LH and T after LHRH injection were similar between HP and LP rams (P greater than .05). These results show that the effects of the ewe on LH secretion of rams depend on length of the exposure period and sexual activity of the male.  相似文献   

19.
Effects of domperidone, a peripheral dopamine receptor antagonist, on secretion of LH and prolactin were studied during the luteal phase and following administration of PGF2 alpha. Since hyperprolactinemia has been reported to inhibit secretion of LH in ewes, effects of thyrotropin-releasing hormone (TRH) also were examined. Ewes 8-10 days post-estrus were assigned to be treated with: 1) vehicle (n = 5); 2) 0.3 mg domperidone (n = 6); 3) 1.0 mg domperidone (n = 6); 4) 3 micrograms TRH (n = 6); or 5) 10 micrograms TRH (n = 6) every 4 hours for 60 hr. Luteal regression was induced with PGF2 alpha at 12 hr after initiation of treatments. During the luteal phase, pulses of LH were more frequent (P less than .05) and the amplitudes of these were higher (P less than .05) in ewes treated with domperidone or TRH than in control ewes. These changes in LH occurred even though each treatment elevated markedly concentrations of prolactin in plasma. After induction of luteal regression, mean of LH and frequency of LH discharges were similar in all groups. However, in ewes treated with the 1.0 mg/4 hr dose of domperidone the pulse amplitude was greater than in the other groups (2.3 vs 1.1 ng/ml). Dose-response relationships and the magnitude of the prolactin release following domperidone or TRH varied with time. Treatments did not affect the timing of the LH surge or the increase in progesterone associated with the subsequent cycle.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

20.
The goal of this study was to determine the effects of short-term feed withdrawal on reproductive and metabolic hormones during the luteal phase of the estrous cycle in mature ewes. Mature ewes observed in estrus were assigned randomly to control and fasted groups (n = 10 per group Trials 1 and 2). For Trials 1 and 2, control ewes had ad libitum access to feed, whereas fasted ewes were not fed from d 7 through 11 of their estrous cycle; on d 12, all ewes were treated with 10 mg of PGF2alpha, and fasted ewes were gvien ad libitum access to feed. For Trial 1, blood samples were collected daily through fasting and at 2-h intervals following PGF2alpha for 72 h. Serum concentrations of insulin (P < or = 0.002) and IGF-I (P < or = 0.01), but not GH (P > or = 0.60), were decreased during fasting compared with fed ewes. Serum concentrations of 29 (P = 0.02) and 34 kDa (P = 0.04) IGFBP were greater in fasted ewes at 96 h after initiation of fasting than in control ewes. Two control and four fasted ewes in Trial 1 did not exhibit a preovulatory surge release of LH by 72 h. Therefore, Trial 2 was conducted so that the timing of the LH surge could be predicted following the collection of blood samples at 2-h intervals for 112 h and then at 6-h intervals until 178 h following PGF2alpha administration and realimentation. The magnitude of the preovulatory LH surge in Trial 2 was decreased (P = 0.009) and delayed (P = 0.04), and serum concentrations of estradiol were diminished (P < or = 0.03) 12 h before the LH surge in fasted ewes. Ovulation rates were not influenced (P > or = 0.32) by fasting in Trials 1 and 2. Serum concentrations of progesterone in both Trials 1 and 2 were, however, greater (P < 0.001) in fasted than in control ewes. A third trial with ovariectomized ewes was conducted to determine whether the increased serum concentrations of progesterone observed in fasted ewes during Trials 1 and 2 were ovarian-derived. Ovariectomized ewes were implanted with progesterone-containing intravaginal implants and allotted to control (n = 5) or fasted (n = 5) treatment groups and fed as described for Trials 1 and 2. Similar to intact ewes, serum concentrations of progesterone were approximately twofold greater (P < 0.001) in fasted than in control implanted ovariectomized ewes. In summary, feed withdrawal for 5 d during the luteal phase of the estrous cycle increased serum concentrations of progesterone and evoked endocrine changes that could perturb the subsequent estrous cycle.  相似文献   

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