Ward M A, Neville T L, Reed J J, Taylor J B, Hallford D M, Soto-Navarro S A, Vonnahme K A, Redmer D A, Reynolds L P, Caton J S
Center for Nutrition and Pregnancy and Animal and Range Sciences Department, North Dakota State University, Fargo 58105, USA.
J Anim Sci. 2008 May;86(5):1254-62. doi: 10.2527/jas.2007-0509. Epub 2008 Feb 13.
The objective of these studies was to evaluate the effects of dietary restriction and Se on maternal and fetal metabolic hormones. In Exp. 1, pregnant ewe lambs (n = 32; BW = 45.6 +/- 2.3 kg) were allotted randomly to 1 of 4 treatments. Diets contained (DM basis) either no added Se (control), or supranutritional Se added as high-Se wheat at 3.0 mg/kg (Se-wheat), or sodium selenate at 3 (Se3) and 15 (Se15) mg/kg of Se. Diets (DM basis) were similar in CP (15.5%) and ME (2.68 Mcal/kg). Treatments were initiated at 50 +/- 5 d of gestation. The control, Se-wheat, Se3, and Se15 treatments provided 2.5, 75, 75, and 375 microg/kg of BW of Se, respectively. Ewe jugular blood samples were collected at 50, 64, 78, 92, 106, 120, and 134 d of gestation. Fetal serum samples were collected at necropsy on d 134. In Exp. 2, pregnant ewe lambs (n = 36; BW 53.8 +/- 1.3 kg) were allotted randomly to treatments in a 2 x 2 factorial arrangement. Factors were nutrition (control, 100% of requirements vs. restricted nutrition, 60% of control) and dietary Se (adequate Se, 6 microg/kg of BW vs. high Se, 80 microg/kg of BW). Selenium treatments were initiated 21 d before breeding, and nutritional treatments were initiated on d 64 of gestation. Diets were 16% CP and 2.12 Mcal/kg of ME (DM basis). Blood samples were collected from the ewes at 62, 76, 90, 104, 118, 132, and 135 d of gestation. Fetal blood was collected at necropsy on d 135. In Exp.1, dietary Se source and concentration had no effect (P > 0.17) on maternal and fetal serum IGF-I, triiodothyronine (T(3)), or thyroxine (T(4)) concentrations. Selenium supplementation increased (P = 0.06) the T(4):T(3) ratio vs. controls. In Exp. 2, dietary Se had no impact (P > 0.33) on main effect means for maternal and fetal serum IGF-I, T(3), or T(4) concentrations from d 62 to 132; however, at d 135, high-Se ewes had lower (P = 0.01) serum T(4) concentrations than adequate-Se ewes. A nutrition by Se interaction (P = 0.06) was detected for the T(4):T(3) ratios; ewes fed restricted and adequate-Se diets had greater (P = 0.10) T(4):T(3) ratios compared with the other treatments. Nutrient-restricted ewes had lower (P < 0.05) serum IGF-I, T(3), and T(4) concentrations. Fetal serum IGF-I concentrations were lower (P = 0.01) in restricted-vs. control-fed ewes; however, fetal T(3) and T(4) concentrations were unaffected (P > 0.13) by dietary Se or maternal plane of nutrition. These data indicate that dietary Se may alter maternal T(4):T(3) ratios. In addition, nutrient restriction during gestation reduces maternal IGF-I, T(3), and T(4) and fetal IGF-I concentrations.
这些研究的目的是评估限饲和硒对母羊及胎儿代谢激素的影响。在试验1中，将怀孕的青年母羊（n = 32；体重 = 45.6 ± 2.3 kg）随机分配到4种处理中的1种。日粮（以干物质计）要么不添加硒（对照），要么添加超营养水平的硒，即添加3.0 mg/kg的高硒小麦（硒小麦），或者添加3（Se3）和15（Se15）mg/kg的亚硒酸钠。日粮（以干物质计）的粗蛋白（CP）含量（15.5%）和代谢能（ME）含量（2.68 Mcal/kg）相似。处理在妊娠50 ± 5 d开始。对照、硒小麦、Se3和Se15处理分别提供2.5、75、75和375 μg/kg体重的硒。在妊娠50、64、78、92、106、120和134 d采集母羊颈静脉血样。在134 d剖检时采集胎儿血清样本。在试验2中，将怀孕的青年母羊（n = 36；体重53.8 ± 1.3 kg）随机分配到2×2析因设计的处理中。因素为营养（对照，满足100%需求 vs. 限饲，对照的60%）和日粮硒（适宜硒，6 μg/kg体重 vs. 高硒，80 μg/kg体重）。硒处理在配种前21 d开始，营养处理在妊娠64 d开始。日粮粗蛋白含量为16%，代谢能为2.12 Mcal/kg（以干物质计）。在妊娠62、76、90、104、118、132和135 d采集母羊血样。在135 d剖检时采集胎儿血样。在试验1中，日粮硒源和浓度对母羊和胎儿血清胰岛素样生长因子-I（IGF-I）、三碘甲状腺原氨酸（T(3)）或甲状腺素（T(4)）浓度无影响（P > 0.17）。与对照相比，补充硒使T(4):T(3)比值升高（P = 0.06）。在试验2中，从妊娠62 d至132 d，日粮硒对母羊和胎儿血清IGF-I、T(3)或T(4)浓度的主效应均值无影响（P > 0.33）；然而，在135 d，高硒母羊的血清T(4)浓度低于适宜硒母羊（P = 0.01）。检测到T(4):T(3)比值存在营养与硒的交互作用（P = 0.06）；与其他处理相比，限饲且硒适宜的母羊T(4):T(3)比值更高（P = 0.10）。营养受限的母羊血清IGF-I、T(3)和T(4)浓度较低（P < 0.05）。与对照饲养的母羊相比，限饲母羊所产胎儿的血清IGF-I浓度较低（P = 0.01）；然而，胎儿T(3)和T(4)浓度不受日粮硒或母羊营养水平的影响（P > 0.13）。这些数据表明，日粮硒可能改变母羊的T(4):T(3)比值。此外，妊娠期间的营养限制会降低母羊的IGF-I、T(3)和T(4)以及胎儿的IGF-I浓度。
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