动物营养学报    2019, Vol. 31 Issue (9): 4099-4109    PDF    
山羊妊娠前期和后期采食量限制对母体血清、羊水和尿囊液中氨基酸组成的影响
李西林1,2 , 李恒芝3 , 贺志雄1 , 谭支良1,4 , 颜琼娴1,5     
1. 中国科学院亚热带农业生态研究所, 亚热带农业生态过程重点实验室, 畜禽养殖污染控制与资源化技术国家工程实验室, 湖南省畜禽健康养殖工程技术研究中心, 农业部中南动物营养与饲料科学观测实验站, 动物营养生理与代谢过程湖南省重点实验室, 长沙 410125;
2. 中国科学院大学, 北京 100049;
3. 南京农业大学动物科学技术学院, 南京 210095;
4. 湖南省畜禽安全生产协同创新中心, 长沙 410128;
5. 湖南省植物功能成分利用协同创新中心, 长沙 410128
摘要: 本试验旨在研究山羊妊娠前期和后期采食量限制对母体血清、羊水和尿囊液中氨基酸(AA)组成的影响。在妊娠前期(第26~65天)和后期(第96~135天),分别将12只年龄[(2.0±0.3)岁]、胎次(2胎)和体重相近的怀孕湘东黑山羊随机分配到对照组(n=6,自由采食)和采食量限制组(n=6,40%采食量限制),妊娠第65天和135天,检测母体血清、羊水和尿囊液中AA含量。结果显示:妊娠前期,与对照组相比,采食量限制组胎儿的体重、体长和胸围显著增加(P < 0.05),血清中缬氨酸(Val)、天冬氨酸(Asp)、脯氨酸(Pro)、总必需氨基酸(EAA)和总非必需氨基酸(NEAA)含量显著降低(P < 0.05),羊水中Val、酪氨酸(Tyr)和赖氨酸(Lys)含量显著降低(P < 0.05),尿囊液中苏氨酸(Thr)、蛋氨酸(Met)、丝氨酸(Ser)和甘氨酸(Gly)含量显著增加(P < 0.05)。妊娠后期,与对照组相比,采食量限制组的胎儿体重显著降低(P < 0.05),血清中Lys、Asp、谷氨酸(Glu)和Pro含量显著降低(P < 0.05),羊水中总EAA、总NEAA和各AA含量也显著降低(P < 0.05),尿囊液中Glu含量显著降低,尿囊液中Pro含量显著增加(P < 0.05)。由此可见,妊娠前期采食量限制会促进胎儿的生长,而妊娠后期采食量限制会抑制胎儿的生长,不同妊娠期采食量限制对母体血液及子宫内AA代谢的影响存在差异。
关键词: 氨基酸    采食量限制    胎儿生长    羊水    尿囊液    山羊    
Maternal Amino Acid Composition in Serum, Amniotic Fluid and Allantoic Fluid Affected by Nutrient Restriction of Goats during Early and Late Gestations
LI Xilin1,2 , LI Hengzhi3 , HE Zhixiong1 , TAN Zhiliang1,4 , YAN Qiongxian1,5     
1. Institute of Subtropical Agriculture, Chinese Academy of Sciences, Key Laboratory for Agro-Ecological Processes in Subtropical Region, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production, Hunan Research Center of Livestock & Poultry Sciences, South Central Experimental Station of Animal Nutrition and Feed Science in the Ministry of Agriculture, Hunan Provincial Key Laboratory of Nutritional Physiology and Metabolic Process, Changsha 410125, China;
2. University of Chinese Academy of Sciences, Beijing 100049, China;
3. College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China;
4. Hunan Co-Innovation Center of Animal Production Safety, Changsha 410128, China;
5. Hunan Co-Innovation Center for Utilization of Botanical Functional Ingredients, Changsha 410128, China
Abstract: This experiment was conducted to investigate the effects of nutrient restriction of goats during early and late gestations on maternal amino acid (AA) composition in serum, amniotic fluid. In early (the 26th to 65th days) and late gestation (the 96th to 135th days), twelve pregnant Xiangdong black goats with similar age[(2.0±0.3) years], parity (2 parities) and body weight were randomly assigned to control group (n=6, ad libitum) and feed intake restricted group (n=6, 40% feed intake restriction). The content of AA in maternal serum, amniotic fluid and allantoic fluid were measured on the 65th and 135th days of pregnancy. The results showed as follows:in early gestation, compared with the control group, the body weight, body length and thoracic circumference of fetuses in feed intake restricted group were significantly increased (P < 0.05), the contents of valine (Val), aspartic acid (Asp), proline (Pro), total essential amino acids (EAA) and total non-essential amino acids (NEAA) in serum were significantly decreased (P < 0.05), the contents of Val, tyrosine (Tyr) and lysine (Lys) in amniotic fluid were significantly decreased (P < 0.05), and the contents of threonine (Thr), methionine (Met), serine (Ser) and glycine (Gly) in allantoic fluid were significantly increased (P < 0.05). In late gestation, compared with the control group, the body weight of fetuses in feed intake restricted group was significantly decreased (P < 0.05), the contents of Lys, Asp, glutamic acid (Glu) and Pro in serum were significantly decreased (P < 0.05), the contents of total EAA, total NEAA and each AA in amniotic fluid were significantly decreased (P < 0.05), the content of Glu in allantoic fluid was significantly decreased (P < 0.05), and the content of Pro in allantoic fluid was significantly increased (P < 0.05). In summary, feed intake restriction during early gestation promotes fetal growth, while inhibits fetal growth during late gestation; feed intake restriction during early and late gestations probably induces some extent variation in AA metabolism of maternal blood and uterus.
Key words: amino acids    feed intake restriction    fetal growth    amniotic fluid    allantoic fluid    goats    

妊娠期间,胎儿的组织和器官会出现重编程发育,以确保自身在营养有限的子宫环境中增加存活率[1]。低蛋白质或低能量或二者兼有的营养不良会对胎儿产生短期或长期的重编程发育影响[2-6]。母体的营养限制也会影响营养物质从母体到胎儿的运移[7-8],导致后代出生时体重过轻。因此,探究由母体营养不良引起的胎儿编程的潜在机理至关重要。

母体血液中的氨基酸(AA)和葡萄糖是胎儿生长过程中特别重要的营养成分[9-10]。母体血液AA通过胎盘运输进入胎儿体内以支持胎儿生长[11-12]。据报道,羊水中的AA主要来源于妊娠前期的母体胎盘和胎儿之间的物质循环,尿囊液中的AA来自胎儿和母体分泌物[13]。前期研究表明,母体AA含量与胎儿生长指标呈负相关,出生胎儿体重较大时,其母体AA含量降低,母体AA含量的变化解释了34%的出生胎儿体重的变化[14-15]。因此,研究母体体液中AA组成将有助于揭示特定营养供应与后代发育的关系。妊娠前期,在功能性胎盘发育之前,胚胎的营养供应由子宫壁的分泌物提供;此阶段胎羊的绝对生长状态相对较低,羊水中的AA含量在妊娠第2个月发生显著变化[16]。在妊娠后期,母体营养不良使胎儿体重迅速增加,母体尿囊液和羊水中AA的子宫通量降低[7, 17],胎盘血液循环系统功能和营养吸收能力提升[18]。Satterfield等[19]研究表明,妊娠第115天,营养限制的母羊羊水和尿囊液中总AA含量显著降低,其胎羊体重也显著降低;同时,前期研究还表明胎儿发育和羊水、尿囊液中AA含量的变化随着妊娠期的不同而不同。Kwon等[16]研究表明,妊娠前期,胎羊绝对生长速度较低,羊水中缬氨酸(Ala)、谷氨酸(Glu)、甘氨酸(Gly)和丝氨酸(Ser)含量最丰富;尿囊液中Ala、瓜氨酸(Cit)和Glu含量升高;妊娠后期,胎羊绝对生长速度较快,羊水中脯氨酸(Pro)和苏氨酸(Thr)含量下降,丙氨酸(Ala)、精氨酸(Arg)、Cit和Glu含量升高;尿囊液中Ser含量的增加与胎儿体重的增加密切相关。

放牧状态下,饲草季节性供应不均衡和寄生虫感染[20]是引起妊娠期母体营养不良的主要原因,而妊娠期间营养不良对AA在母体与胎儿间循环和胎儿编程发育之间的关系尚不清楚。本研究提出山羊母体采食量限制可能改变母体血液、羊水和尿囊液中的AA含量,并且这种影响会随着不同的妊娠阶段而改变,从而改变胎儿的生长发育的假设。因此,本试验旨在研究山羊妊娠前期(第26~65天)和后期(第96~135天)采食量限制(限饲40%的采食量)对胎儿的发育以及母体血清、羊水和尿囊液中AA含量的影响。

1 材料与方法

所有动物试验程序均按照中国科学院亚热带农业研究所动物保护委员会批准的指导原则进行。

1.1 妊娠前期采食量限制试验设计及饲养管理(试验1)

选择年龄[(2.0±0.3)岁]、胎次(2胎)和体重[(31.2±6.1) kg]相近的20只雌性湘东黑山羊作为试验动物,采用同期发情和人工授精的方式以确保母羊怀孕日期的一致性。通过先注射孕激素,然后注射马绒毛膜促性腺激素来实现发情同步。所有试验母羊都接受来自同一只公山羊的解冻精液,人工授精第2天被认为是妊娠的第1天。妊娠第1~20天,怀孕母羊被饲养在普通的牧场,不再补饲。然后将它们分别单栏饲喂,并适应试验饲粮3 d(第23~25天)。第25天将12只超声检查为双胎妊娠的试验山羊随机分为2组:对照组(n=6,自由采食)和采食量限制组(n=6,40%采食量限制),妊娠检查诊断标准是B超扫描仪显示屏存在2个孕囊液性暗区[21]。正式试验期为妊娠第26~65天,按照《肉羊饲养标准》(NY/T 816—2004)[22],对照组饲粮满足妊娠山羊100%的代谢能和粗蛋白质需求,采食量限制组的营养需求为对照组的60%,试验饲粮组成及营养水平见表 1。每隔1 d收获1次芒草,切成2 cm左右长。每只怀孕的山羊每天饲喂850~950 g干物质。每天分别在08:30和17:00饲喂并记录采食量,所有山羊自由饮水。饲喂量随妊娠天数增加,每7 d调升5%,采食量限制组饲粮添加量为对照组饲粮添加量的60%。

表 1 试验饲粮组成及营养水平(干物质基础) Table 1 Composition and nutrient levels of experimental diets (DM basis)
1.2 妊娠后期采食量限制试验设计及饲养管理(试验2)

选择年龄[(2.0±0.3)岁]、胎次(2胎)和体重[(36.0±5.4)] kg相近的12只同步受孕(方法与试验1相同)雌性湘东黑山羊,随机分成2组:对照组(n=6,自由采食)和采食量限制组(n=6,40%采食量限制)。试验1和试验2非同一批母羊。妊娠第90天进行超声检查确保双胎妊娠。母羊在妊娠第90天前被饲养在普通的牧场,不再补饲。经过5 d的适应期后开始正式试验,正式试验期为妊娠第96~135天,试验妊娠山羊的管理和饲粮喂养与试验1相同。试验饲粮组成及营养水平见表 1。每只妊娠山羊每天饲喂1 150~1 250 g干物质。每天分别在08:30和17:00饲喂并记录采食量,所有山羊自由饮水。饲喂量随妊娠天数增加,每7 d调升5%,采食量限制组饲粮添加量亦为对照组饲粮添加量的60%。

1.3 饲粮营养成分分析

按照张丽英[23]方法对饲料样品(精料和芒草)和饲粮干物质、粗蛋白质(CP)、钙(Ca)、磷(P)、中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)和粗纤维(CF)含量进行测定。

1.4 样本采集

试验结束后,试验山羊空腹12 h,于妊娠前期第65天和妊娠后期第135天使用无菌注射器从母羊颈静脉收集血液,室温放置2 h,在4 ℃条件下以3 000×g离心15 min,收集血清,-80 ℃冻存。所有试验山羊实施安乐死,剖腹后收集羊水和尿囊液,在4 ℃条件下以3 000×g离心15 min,分装上清液并-80 ℃冻存。获取胎儿后称量胎儿体重,并用卷尺测量胎儿的体长(从头部到臀部)、胸围和脐围。妊娠前期限饲试验收集到24只胎儿(11只雌性,13只雄性),妊娠后期限饲试验收集到24只胎儿(14只雌性,10只雄性)。

1.5 样品预处理与测定

向血清样本中加入0.08 g/mL磺基水杨酸,4 ℃静置12 h以沉淀出蛋白质,在4 ℃条件下10 000×g离心15 min,收集上清液并经0.45 μm微孔膜过滤,将滤液注入上机瓶中,通过L-8800型氨基酸自动分析仪(日本日立)测定滤液中游离的AA含量,测定步骤参考Li等[24]的程序。羊水样品预处理程序与血清处理方法相同。尿囊液先用0.01 mol/mL盐酸溶液稀释10倍,后续步骤与血清样品相同。

1.6 数据分析

所有试验数据经过Excel 2016软件整理后,采用SAS 9.2软件进行单因子方差分析,分析母体血液、羊水和尿囊液中AA含量的所有数据。P<0.05表示差异显著,0.05<P<0.10表示差异有显著趋势。

2 结果 2.1 妊娠前期胎儿生长及AA谱(试验1)

表 2可见,在试验1结束时,采食量限制组山羊精料、草料和饲粮养分(干物质、CP、总能、NDF、ADF和CF)采食量比对照组低40%左右(P < 0.05)。由表 3可见,采食量限制组胎儿体长、体重、胸围均显著高于对照组(P < 0.05),而脐围有升高的趋势(0.05<P<0.10)。

表 2 母羊妊娠前期、后期干物质和养分采食量 Table 2 Dry matter and nutrient feed intake of goats during early and late gestations
表 3 妊娠前期、后期营养限制对胎儿生长的影响 Table 3 Effects of nutrient restriction on growth of fetus during early and late gestations

在妊娠前期,由表 4可见,采食量限制组血清中缬氨酸(Val)、天冬氨酸(Asp)、Pro、总必需氨基酸(EAA)和总非必需氨基酸(NEAA)含量均显著低于对照组(P < 0.05),同时血清中Arg含量有降低的趋势(0.05<P<0.10);由表 5可见,采食量限制组羊水中Val、酪氨酸(Tyr)和赖氨酸(Lys)含量均显著低于对照组(P < 0.05),羊水中异亮氨酸(Ile)、亮氨酸(Leu)、Arg、Ala和Pro含量有降低的趋势(0.05<P<0.10);由表 6可见,采食量限制组尿囊液中Thr、蛋氨酸(Met)、Ser和Gly含量均显著高于对照组(P < 0.05),尿囊液中Arg、总EAA、总NEAA和总AA含量有升高的趋势(0.05<P<0.10)。

表 4 妊娠前期、后期营养限制对母体血清中AA含量的影响 Table 4 Effects of nutrient restriction on serum AA contents of maternal goats during early and late gestations
表 5 妊娠前期、后期营养限制对母体羊水中AA含量的影响 Table 5 Effects of nutrient restriction on amniotic fluid AA contents of maternal goats during early and late gestations
表 6 妊娠前期、后期营养限制对母体尿囊液中AA含量的影响 Table 6 Effects of nutrient restriction on allantoic fluid AA contents of maternal goats during early and late gestations
2.2 妊娠后期胎儿生长及AA谱(试验2)

表 2可见,在试验2结束时,采食量限制组的山羊精料、草料和饲粮养分(干物质、CP、总能、NDF、ADF和CF)采食量(以DM计)比对照组低40%左右(P < 0.05)。由表 3可见,采食量限制组胎儿的体重显著低于对照组(P < 0.05),胸围有降低的趋势(0.05<P<0.10)。

在妊娠后期,由表 4可见,采食量限制组血清中Lys、Asp、Glu和Pro含量均显著低于对照组(P < 0.05);由表 5可见,采食量限制组羊水中各AA、总EAA、总NEAA和总AA含量均显著低于对照组(P < 0.05);由表 6可见,采食量限制组尿囊液中Glu含量显著低于对照组(P < 0.05),尿囊液中Pro含量显著高于对照组(P < 0.05)。

3 讨论

绵羊是宫内生长受限研究较多的模型动物,但截止目前,关于AA在妊娠反刍动物的羊水和尿囊液的研究还很有限。在本研究中,妊娠前期采食量限制组母羊的养分采食量占对照组的62%~70%,说明试验采食过程管理得到了有效控制,特别是妊娠后期采食量限制的管理。本试验发现在妊娠前期,采食量限制组的胎儿在营养限制结束时具有更大的体重、体长和胸围。这些结果与Osgerby等[27]的研究结果部分一致,其中也观察到妊娠前期母绵羊营养受限会导致胎儿胸围增加;然而,这与Nishina等[28]的研究结果有所不同,其在绵羊妊娠前期进行营养限制后发现胎儿体重大小没有差异,这可能与营养限制的持续时间和物种的差异有关。妊娠前期营养限制促进胎儿生长可以从2个方面来解释:母羊减少能量消耗,刺激生长因子的表达,影响胎盘以及胎儿生长和新陈代谢,以适应营养限制[25, 29-30];同时,母羊在这一阶段的情况不稳定,妊娠反应不规律地发生,但是营养限制可以缓解妊娠反应,从而刺激胎儿的生长[31]。在妊娠后期观察到胎儿体重的减少,这与我们之前的研究[32]、Stephenson等[33]和Sebert等[34]的研究结果一致,表明与前期限制相比,妊娠后期的营养限制更易诱导胎儿出现宫内发育迟缓。

通过胎盘从母体转运到胎儿的血清中AA对于胎儿生长至关重要,AA的运移受限制与胎儿生长受损密切相关[35]。在反刍动物妊娠后期,AA可提供约55%的胎儿生长能量需求[36-37]。母体营养消耗与摄入不平衡(如饲粮蛋白质和能量限制)会影响母体能量利用和AA的代谢状态,进而影响胎儿的生长发育[16, 38]。相关研究表明,Val、Ala、Glu、Tyr、His和Cit在妊娠前期胎儿的生长中起重要作用[31]。在本研究中,母山羊的采食量限制导致妊娠前期血清中Val、Asp和Pro含量下降,妊娠后期血清中Lys、Glu、Asp和Pro含量下降。这表明妊娠前期和后期的营养限制对母体AA代谢状态是不同的,Val、Asp和Pro对胎儿的早期生长更为重要,而Lys、Asp、Glu和Pro供应不足可能是山羊妊娠后期胎儿发育迟缓的关键因素。妊娠前期和后期营养限制均使母体血清中Asp和Pro含量降低,表明这2种NEAA对营养限制的敏感性高于其他NEAA。

羊水可以为胎儿生长发育提供游离的AA和相关的生物分子,其中的部分物质来自于胎盘,因此羊膜腔内的羊水成分受到胎儿和胎盘的影响[39]。胎儿通常通过吞咽羊水来获得游离的AA,若禁止胎儿吞咽羊水可以导致胎儿肠道发育受限,表明羊水中的AA是胎儿发育所必需的[40]。本试验中,在妊娠前期营养限制结束时,羊水中Val、Tyr和Lys含量降低,这表明妊娠前期营养限制使从胎盘转运到羊水中的Val、Tyr和Lys受到限制,这与母羊血液中的Val含量降低的现象是部分协同的。Dunford等[38]的研究发现,妊娠前期(第1~65天)母羊蛋白质和能量限制能够影响胎儿的鸟氨酸(Orn)循环,羊水中的Orn含量显著降低。而本研究中,羊水中Orn的含量没有受到营养限制的影响,这可能是由于妊娠营养限制期的选择和营养限制程度的差异。Mayhew等[41]研究发现,在胎儿生长受限的情况下,体内和体外数据显示胎盘表面积和通透性常数显著降低,导致胎盘扩散转运能力的整体降低。Strakovsky等[42]研究表明,妊娠期间的低蛋白质饮食可以激活胎盘AA反应通路,提高后代对营养成分的利用。本试验中,妊娠后期羊水中的各AA含量均下降,表明营养限制使从胎盘转运到羊水中的所有AA受到了限制,这可能与母体营养物质供给不足使胎盘转运能力降低和胎羊对羊水中AA的利用率增加有关。由此可见,不同妊娠期母体采食量限制导致的各AA含量变化有所不同,与妊娠前期相比,妊娠后期母体采食量限制可以全面改变胎盘中的AA运输。

尿囊液中AA含量与胎儿的生长有关。在妊娠前期,本研究发现采食量限制组山羊尿囊液中Thr、Met、Ser和Gly含量增加。Kwon等[7]的研究显示,在妊娠第28~78天实施50%营养限制的绵羊尿囊液中Gly含量增加,Ser含量降低。结果差异可能与营养限制程度和试验周期有关。妊娠前期尿囊液中的AA变异情况表明Thr、Met、Ser和Gly对营养限制更敏感,胎儿可能代谢排出较多的这些AA。在妊娠后期,限制组尿囊液中Glu含量降低,Pro含量增加,这表明胎儿可以利用较多的Glu进行自身生长并在尿囊液中排出更多的Pro。Wu等[43]报道猪和羊妊娠期间尿囊液中Arg非常丰富,Arg可代谢为Pro,Pro在子宫和胎盘参与多胺的合成,多胺是基因表达的调节因子,提出Arg在胚胎发育过程中发挥重要作用的假设。本试验中,营养限制造成妊娠前期和后期母羊血液和羊水中Pro含量均降低,而排泄到尿囊中Pro含量却升高了,这可能与Arg的代谢有关。此外,结果显示Ser是妊娠后期尿囊液中最丰富的AA,Kwon等[16]在妊娠第140天绵羊尿囊液中也发现了相同的现象。

4 结论

妊娠前期采食量限制会促进胎儿的生长,而妊娠后期采食量限制会抑制胎儿的生长,不同妊娠期采食量限制对母体血液及子宫内AA代谢的影响存在差异。

参考文献
[1]
BARKER D J. The long-term outcome of retarded fetal growth[J]. Clinical Obstetrics and Gynecology, 1997, 40(4): 853-863. DOI:10.1097/00003081-199712000-00019
[2]
FOWDEN A L, SFERRUZZI-PERRI A N, COAN P M, et al. Placental efficiency and adaptation:endocrine regulation[J]. The Journal of Physiology, 2009, 587(14): 3459-3472. DOI:10.1113/jphysiol.2009.173013
[3]
HE Z X, SUN Z H, BEAUCHEMIN K A, et al. Effect of protein or energy restriction during late gestation on hormonal and metabolic status in pregnant goats and postnatal male offspring[J]. Animal, 2015, 9(11): 1843-1851. DOI:10.1017/S1751731115001147
[4]
HE Z X, SUN Z H, TAN Z L, et al. Effects of maternal protein or energy restriction during late gestation on antioxidant status of plasma and immune tissues in postnatal goats[J]. Journal of Animal Science, 2012, 90(12): 4319-4326. DOI:10.2527/jas.2012-5088
[5]
HE Z X, SUN Z H, YANG W Z, et al. Effects of maternal protein or energy restriction during late gestation on immune status and responses to lipopolysaccharide challenge in postnatal young goats[J]. Journal of Animal Science, 2014, 92(11): 4856-4864. DOI:10.2527/jas.2014-7904
[6]
MCMILLEN I C, ROBINSON J S. Developmental origins of the metabolic syndrome:prediction, plasticity, and programming[J]. Physiological Reviews, 2005, 85(2): 571-633. DOI:10.1152/physrev.00053.2003
[7]
KWON H, FORD S P, BAZER F W, et al. Maternal nutrient restriction reduces concentrations of amino acids and polyamines in ovine maternal and fetal plasma and fetal fluids[J]. Biology of Reproduction, 2004, 71(3): 901-908. DOI:10.1095/biolreprod.104.029645
[8]
METZLER-ZEBELI B U, LANG I S, GÖRS S, et al. High-protein-low-carbohydrate diet during pregnancy alters maternal plasma amino acid concentration and placental amino acid extraction but not fetal plasma amino acids in pigs[J]. British Journal of Nutrition, 2012, 108(12): 2176-2189. DOI:10.1017/S0007114512000414
[9]
CETIN I, RONZONI S, MARCONI A M, et al. Maternal concentrations and fetal-maternal concentration differences of plasma amino acids in normal and intrauterine growth-restricted pregnancies[J]. American Journal of Obstetrics and Gynecology, 1996, 174(5): 1575-1583. DOI:10.1016/S0002-9378(96)70609-9
[10]
JOBGEN W S, FORD S P, JOBGEN S C, et al. Baggs ewes adapt to maternal undernutrition and maintain conceptus growth by maintaining fetal plasma concentrations of amino acids[J]. Journal of Animal Science, 2007, 86(4): 820-826.
[11]
BATTAGLIA F C, REGNAULT T R H. Placental transport and metabolism of amino acids[J]. Placenta, 2001, 22(2/3): 145-161.
[12]
SENGERS B G, PLEASE C P, LEWIS R M. Computational modelling of amino acid transfer interactions in the placenta[J]. Experimental Physiology, 2010, 95(7): 829-840. DOI:10.1113/expphysiol.2010.052902
[13]
BAETZ A L, HUBBERT W T, GRAHAM C K. Developmental changes of free amino acids in bovine fetal fluids with gestational age and the interrelationships between the amino acid concentrations in the fluid compartments[J]. Reproduction, 1975, 44(3): 437-444. DOI:10.1530/jrf.0.0440437
[14]
DUGGLEBY S L, JACKSON A A. Higher weight at birth is related to decreased maternal amino acid oxidation during pregnancy[J]. The American Journal of Clinical Nutrition, 2002, 76(4): 852-857. DOI:10.1093/ajcn/76.4.852
[15]
EVANS R W, POWERS R W, NESS R B, et al. Maternal and fetal amino acid concentrations and fetal outcomes during pre-eclampsia[J]. Reproduction, 2003, 125(6): 785-790. DOI:10.1530/rep.0.1250785
[16]
KWON H, SPENCER T E, BAZER F W, et al. Developmental changes of amino acids in ovine fetal fluids[J]. Biology of Reproduction, 2003, 68(5): 1813-1820. DOI:10.1095/biolreprod.102.012971
[17]
LEMLEY C O, CAMACHO L E, MEYER A M, et al. Dietary melatonin supplementation alters uteroplacental amino acid flux during intrauterine growth restriction in ewes[J]. Animal, 2013, 7(9): 1500-1507. DOI:10.1017/S1751731113001006
[18]
LEKATZ L A, SWANSON T J, CAMACHO L E, et al. Maternal metabolizable protein restriction during late gestation on uterine and umbilical blood flows and maternal and fetal amino acid concentrations near term in sheep[J]. Animal Reproduction Science, 2015, 158: 115-125. DOI:10.1016/j.anireprosci.2015.05.009
[19]
SATTERFIELD M C, BAZER F W, SPENCER T E, et al. Sildenafil citrate treatment enhances amino acid availability in the conceptus and fetal growth in an ovine model of intrauterine growth restriction[J]. The Journal of Nutrition, 2010, 140(2): 251-258. DOI:10.3945/jn.109.114678
[20]
TORRES-ACOSTA J F J, HOSTE H. Alternative or improved methods to limit gastro-intestinal parasitism in grazing sheep and goats[J]. Small Ruminant Research, 2008, 77(2/3): 159-173.
[21]
AMER H A. Ultrasonographic assessment of early pregnancy diagnosis, fetometry and sex determination in goats[J]. Animal Reproduction Science, 2010, 117(3/4): 226-231.
[22]
中华人民共和国农业部. 中华人民共和国农业行业标准——肉羊饲养标准(NY/T 816-2004)[J]. 湖南饲料, 2006(6): 9-15.
[23]
张丽英. 饲料分析及饲料质量检测技术[M]. 2版. 北京: 中国农业大学出版社, 2003.
[24]
LI J Y, PIAO C X, JIN H Z, et al. Delayed deproteinization causes methodological errors in amino acid levels in plasma stored at room temperature or -20℃[J]. Asian-Australasian Journal of Animal Sciences, 2009, 22(12): 1703-1708. DOI:10.5713/ajas.2009.90156
[25]
YAN Q X, XU J Z, WU X S, et al. Stage-specific feed intake restriction differentially regulates placental traits and proteome of goats[J]. British Journal of Nutrition, 2018, 119(10): 1119-1132. DOI:10.1017/S0007114518000727
[26]
LI X P, YAN Q X, TANG S X, et al. Effects of maternal feed intake restriction during pregnancy on the expression of growth regulation, imprinting and epigenetic transcription-related genes in foetal goats[J]. Animal Reproduction Science, 2018, 198: 90-98. DOI:10.1016/j.anireprosci.2018.09.005
[27]
OSGERBY J C, WATHES D C, HOWARD D, et al. The effect of maternal undernutrition on ovine fetal growth[J]. Journal of Endocrinology, 2002, 173(1): 131-141. DOI:10.1677/joe.0.1730131
[28]
NISHINA H, GREEN L R, MCGARRIGLE H H G, et al. Effect of nutritional restriction in early pregnancy on isolated femoral artery function in mid-gestation fetal sheep[J]. The Journal of Physiology, 2003, 553(2): 637-647. DOI:10.1113/jphysiol.2003.045278
[29]
GONZALEZ P N, GASPEROWICZ M, BARBEITO-ANDRÉS J, et al. Chronic protein restriction in mice impacts placental function and maternal body weight before fetal growth[J]. PLoS One, 2016, 11(3): e0152227. DOI:10.1371/journal.pone.0152227
[30]
HELLMUTH C, UHL O, KIRCHBERG F F, et al. Influence of moderate maternal nutrition restriction on the fetal baboon metabolome at 0.5 and 0.9 gestation[J]. Nutrition, Metabolism and Cardiovascular Diseases, 2016, 26(9): 786-796. DOI:10.1016/j.numecd.2016.04.004
[31]
COAD J, AL-RASASI B, MORGAN J. Nutrient insult in early pregnancy[J]. Proceedings of the Nutrition Society, 2002, 61(1): 51-59.
[32]
HE Z X, WU D Q, SUN Z H, et al. Protein or energy restriction during late gestation alters fetal growth and visceral organ mass:an evidence of intrauterine programming in goats[J]. Animal Reproduction Science, 2013, 137(3/4): 177-182.
[33]
STEPHENSON R G A, BIRD A R. Responses to protein plus energy supplements of pregnant ewes eating mature grass diets[J]. Australian Journal of Experimental Agriculture, 1992, 32(2): 157-162. DOI:10.1071/EA9920157
[34]
SEBERT S P, DELLSCHAFT N S, CHAN L L Y, et al. Maternal nutrient restriction during late gestation and early postnatal growth in sheep differentially reset the control of energy metabolism in the gastric mucosa[J]. Endocrinology, 2011, 152(7): 2816-2826. DOI:10.1210/en.2011-0169
[35]
PAOLINI C L, MARCONI A M, RONZONI S, et al. Placental transport of leucine, phenylalanine, glycine, and proline in intrauterine growth-restricted pregnancies[J]. The Journal of Clinical Endocrinology & Metabolism, 2001, 86(11): 5427-5432.
[36]
ANGIOLINI E, FOWDEN A, COAN P, et al. Regulation of placental efficiency for nutrient transport by imprinted genes[J]. Placenta, 2006, 27(Suppl.A): 98-102.
[37]
BELL A W, FERRELL C L, FREETLY H C.Pregnancy and fetal metabolism[M]//DIJKSTRA J, FORBES J M, FRANCE J.Quantitative aspects of ruminant digestion and metabolism.Wallingford, Oxfordshire: CABI, 1993: 405-431.
[38]
DUNFORD L J, SINCLAIR K D, KWONG W Y, et al. Maternal protein-energy malnutrition during early pregnancy in sheep impacts the fetal ornithine cycle to reduce fetal kidney microvascular development[J]. The FASEB Journal, 2014, 28(11): 4880-4892. DOI:10.1096/fj.14-255364
[39]
ZHOU W L, GOSCH G, GUERRA T, et al. Amino acid profiles in first trimester amniotic fluids of healthy bovine cloned pregnancies are similar to those of IVF pregnancies, but not nonviable cloned pregnancies[J]. Theriogenology, 2014, 81(2): 225-229. DOI:10.1016/j.theriogenology.2013.09.012
[40]
TRAHAIR J F, HARDING R. Restitution of swallowing in the fetal sheep restores intestinal growth after midgestation esophageal obstruction[J]. Journal of Pediatric Gastroenterology and Nutrition, 1995, 20(2): 156-161. DOI:10.1097/00005176-199502000-00004
[41]
MAYHEW T M, OHADIKE C, BAKER P N, et al. Stereological investigation of placental morphology in pregnancies complicated by pre-eclampsia with and without intrauterine growth restriction[J]. Placenta, 2003, 24(2/3): 219-226.
[42]
STRAKOVSKY R S, ZHOU D, PAN Y X. A low-protein diet during gestation in rats activates the placental mammalian amino acid response pathway and programs the growth capacity of offspring[J]. The Journal of Nutrition, 2010, 140(12): 2116-2120. DOI:10.3945/jn.110.127803
[43]
WU G Y, BAZER F W, SATTERFIELD M C, et al. Impacts of arginine nutrition on embryonic and fetal development in mammals[J]. Amino Acids, 2013, 45(2): 241-256.