Maternal Nutritional Plane and Endogenous Retroviral Gene Elements, Pregnancy Hormones, and Placental Vascularity and Angiogenic Factors during the Establishment of Pregnancy in Beef Cattle

Abstract

In order to meet the projected food demands by 2050, animal agriculture must increase production of animal products on the same or decreased land area through increased efficiency. Early gestation is one area to increase efficiency in beef production in a twofold manner 1) by increasing the number of calves born due to decreased early embryonic loss and 2) by minimizing detrimental effects due to fetal programming which may decrease offspring growth or reproductive efficiency. Both of which will result in more pounds of beef produced by the same number of cows. Recently, endogenous retroviral elements (ERV), which make up a significant portion of mammalian genomes, have been implicated in vital steps during placentation. The placenta is the source of nutrient, gas, and waste exchange between maternal and fetal circulation which is necessary to support fetal growth. Maternal nutrition influences fetal growth and placental development. Therefore, we hypothesized that ERV envelope genes, syncytin-Rum1 and BERV-K1, as well as pregnancy specific hormones, PSP-B, and IFN-τ will be differentially expressed during critical time points of early pregnancy and maternal nutrition restriction will alter mRNA expression at critical time points. We developed a technique to ovariohysterectomized beef heifers which provides a large animal model to acquire uteroplacental tissues. In year 1, we established basal expression patterns for syncytin-Rum1 and BERV-K1, PSP-B, and IFN-τ within utero-placental tissues during the first 50 d of gestation. In year 2, we determined the effects of 40% global nutrient restriction on the mRNA expression of syncytin-Rum1 and BERV-K1, PSP-B, and IFN-τ on d 16, 34, and 50 of gestation in uteroplacental tissues. These data provide novel evidence of differential expression of endogenous retroviruses (syncytin-Rum1 and BERV-K1), PSP-B, and IFN-τ during early gestation but 40% maternal nutrient restriction had little influence of mRNA expression. However, further work needs to be completed to elucidate functions, mechanisms, and interactions of these genes during early gestation and their importance to the successful establishment of pregnancy.