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The impacts of placental size and vascularity on litter size in the pig.

机译：胎盘大小和血管性对猪产仔数的影响。

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摘要

Prenatal losses in U.S. pig breeds range from 30 to 40%, of which greater than 75% occurs before day 30 of gestation and is thought to result from litter mate asynchrony. Numbers of embryos can be experimentally increased on day 30 postmating by utilizing superovulation and superfetation, however, these females farrow the same number of piglets as untreated controls. These data demonstrate that between day 30 and term there can be significant additional conceptus losses, which has led to the conclusion that uterine capacity (i.e. the number of conceptuses a female's uterus can accommodate) is a major limitation to litter size in the pig. The importance of uterine capacity in the pig may result from the noninvasive epitheliochorial type of placentation in this species, making placental vascularity and the surface area of attachment between the placenta and endometrium limiting factors in nutrient and oxygen exchange. Yorkshire placentae progressively increase in surface area of attachment with only a modest increase in vascularity, whereas the prolific (3 to 4 more piglets per litter than Yorkshire females) Chinese Meishan pig markedly increases placental vascularity, but does not increase surface area of attachment. This dissertation addresses the impacts of changes in placental size and/or vascularity on litter size in these two pig breeds. Placental patterns of vascular endothelial growth factor (VEGF) expression, a potent placental angiogenic and permeability factor, and its receptors (VEGF-R1 and VEGF-R2) were greater in the Meishan compared to Yorkshire conceptuses. Further, a multigenerational selection for increased placental efficiency (fetal weight/placental weight) in our Yorkshire population resulted in larger litter sizes, and conceptuses with increased placental mRNA expression of VEGF and its receptors throughout late gestation. It is hypothesized from these data that pigs with increased litter sizes are those which have increased placental efficiencies associated with an increased VEGF-receptor system.
机译：美国猪品种的产前损失为30％至40％，其中超过75％发生在妊娠第30天之前，并且被认为是由同窝伴侣异步引起的。可以通过超排卵和超胎在实验后第30天通过实验增加胚胎的数量，但是，这些雌性猪的产仔猪数量与未处理的对照组相同。这些数据表明，在第30天到足月之间，可能还会出现其他严重的概念损失，这导致了以下结论：子宫容量（即雌性子宫可以容纳的概念数目）是猪窝大小的主要限制。猪的子宫容量的重要性可能源于该物种的无创上皮性胎盘形成类型，这使得胎盘血管形成以及胎盘与子宫内膜之间的附着表面积限制了养分和氧气交换。约克郡胎盘的附着表面积逐渐增加，而血管仅适度增加，而多产（每窝仔猪比约克郡雌性多3至4头）的中国梅山猪显着增加了胎盘血管，但并未增加附着表面积。本文探讨了这两种猪的胎盘大小和/或血管变化对垫料大小的影响。与约克郡概念相比，梅山地区的血管内皮生长因子（VEGF）表达，胎盘血管生成和通透性因子及其受体（VEGF-R1和VEGF-R2）的胎盘模式更大。此外，在我们的约克郡人群中多代选择以提高胎盘效率（胎儿体重/胎盘重量）导致了更大的产仔数，并且在妊娠后期整个胎盘中VEGF及其受体的胎盘mRNA表达增加。从这些数据中可以推测，窝数增加的猪是与VEGF受体系统增加有关的胎盘效率增加的猪。

著录项

  • 作者

    Vonnahme, Kimberly Ann.;

  • 作者单位

    University of Wyoming.;

  • 授予单位 University of Wyoming.;
  • 学科 Biology Animal Physiology.
  • 学位 Ph.D.
  • 年度 2003
  • 页码 176 p.
  • 总页数 176
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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