Vinsky M D, Paradis F, Dixon W T, Dyck M K, Foxcroft G R
Swine Reproduction-Development Program, Swine Research & Technology Centre, University of Alberta, Edmonton, Alberta, Canada.
Reprod Fertil Dev. 2007;19(5):603-11. doi: 10.1071/rd06116.
Using an established experimental paradigm, feed restriction during the last week of lactation in primiparous sows reduces embryonic growth and development and produces female-specific embryonic mortality by Day 30 of gestation. Because this gender-specific loss of embryos at Day 30 was associated with changes in the variation of markers of epigenetic imprinting, the present study sought to establish the ontogeny of such epigenetic affects. Leucocyte DNA of restrict-fed sows exhibited decreased global methylation during the last week of lactation and during the return to oestrus (P < 0.05), but no associated changes in plasma folate and vitamin B(12). Furthermore, no changes in methylation of blastocyst DNA, embryonic sex ratios or development were evident at Day 6 of gestation that would characterise the underlying defects that reduced female embryo survival by Day 30. However, regardless of treatment, embryo recovery rates and synchrony in embryonic development were associated with the stage of development of the recovered embryos (r = 0.68; P < 0.001). The subset of sows classified as bearing litters with superior embryonic development had lower net energy balance over lactation (P < 0.01) and higher ovulation rates (P < 0.005) compared with sows classified as having poorer embryonic development. Collectively, these data suggest that a subset of litters within restrict-fed sows will be most sensitive to the latent epigenetic mechanisms that ultimately trigger gender-specific loss of embryos by Day 30 of gestation, but that these selective mechanisms are not evident by Day 6 of gestation.
采用既定的实验范式，初产母猪在泌乳期最后一周进行限饲会降低胚胎生长发育，并在妊娠第30天时导致雌性特异性胚胎死亡。由于妊娠第30天时这种特定性别的胚胎损失与表观遗传印记标记变化有关，本研究旨在确定这种表观遗传影响的个体发生过程。限饲母猪的白细胞DNA在泌乳期最后一周及发情期恢复时整体甲基化水平降低（P < 0.05），但血浆叶酸和维生素B12无相关变化。此外，在妊娠第6天时，囊胚DNA甲基化、胚胎性别比例或发育均无明显变化，这些变化可表征导致雌性胚胎在第30天时存活率降低的潜在缺陷。然而，无论处理方式如何，胚胎回收率和胚胎发育同步性都与回收胚胎的发育阶段相关（r = 0.68；P < 0.001）。与胚胎发育较差的母猪相比，被归类为具有优良胚胎发育的仔猪的母猪在泌乳期的净能量平衡较低（P < 0.01），排卵率较高（P < 0.005）。总体而言，这些数据表明，限饲母猪中的一部分仔猪对潜在的表观遗传机制最为敏感，这些机制最终会在妊娠第30天时引发特定性别的胚胎损失，但在妊娠第6天时这些选择机制并不明显。
