Controls of Litter Size—Do Conclusions Drawn from Institutional Research Herds Always Have Relevance to Commercial Swine Production?

Increasing litter size in pigs has been an ongoing concern of many producers because it has the greatest impact on profitability of the swine enterprise. To study the biology of conceptus growth and survival, many models have been used by researchers. It was determined that a major component in limiting litter size results from the impacts of limitations in uterine space (i.e. uterine capacity). Placental efficiency, which is the ratio of a fetus’s weight compared with that of its placenta, has been shown to impact litter size, and is heritable. Selection for breeding animals having a high placental efficiency at term, has been shown to increase litter size. Furthermore, although piglet weight was only slightly decreased in offspring of boars and gilts selected for increased placental efficiency, placental size was profoundly reduced. This reduction in placental size was coupled with an increase in vascularity, thus nutrient and oxygen uptake by the conceptus could be accomplished over a decreased surface area of attachment to the uterine wall. Reproductive data obtained to date have been gathered largely from university swine herds that may have little relevance to commercially used US pig breeds. In contrast to the constant evaluations of physiological changes associated with increased litter size at universities, swine seed stock producers have selected for many generations simply on increased litter size and have not bothered to evaluate the resulting physiological changes associated with increased fecundity. Therefore, it was the objective of this study to investigate the reproductive characteristics of a commercially relevant swine herd in Iowa (PIC Camborough Line) at selected gestational ages. Multiparous sows (ranging from 1 to 14 parities) were slaughtered on days 25, 36, and 44 of gestation, time periods corresponding to intervals which are before, during, and after the time when uterine capacity becomes limiting. At the laboratory, the uterine horns were measured and ovulation rate was determined. Conceptuses were removed and fetal and placental weights were determined. Uterine horn length and ovulation rate did not differ between the three gestational groups. Conceptus number decreased from 15.8 ± 0.6 on day 25 to 12.9 ± 0.5 and 12.1 ± 0.4 on day 36 and day 44 (litter size in this population averages ~11.5 liveborn piglets/litter). Conceptus survival to day 25 was 60.2 ± 0.1%, which then decreased to 50.1 ± 0.1% on day 36 and 46.3 ± 0.1% on day 44. There was a positive correlation between conceptus number and ovulation rate on day 25 but by day 36 this association was lost. Conceptus number was not associated with uterine length on day 25, but by day 36 there was a positive association that remained through day 44. On all three gestation days there was a negative association between conceptus number and placental weight, but no association between conceptus number and fetal weight was observed, indicating that larger litters are comprised of conceptuses having small placentae, but the same sized fetuses. These data indicate that, compared with commonly reported values for university herds (16-18 ovulations), ovulation rate in these mixed parity production animals is extremely high, whereas conceptus survival as estimated from the number of conceptuses divided by the number of ovulations was very low. Additionally, although conceptus number was related to the ovulation rate on day 25, by day 36 the limitations of uterine size began to reduce conceptus number irrespective of ovulation rate. These data suggest that ovulation rate is not a limiting factor in litter size in this line of commercially relevant pigs. In contrast, the higher than expected ovulation rate observed in these pigs resulted in significant embryo losses and early uterine crowding. The consequences of this early conceptus crowding may have detrimental impacts on prenatal and postnatal growth rate and survival

Regulation of IGF-I and porcine oviductal secretory protein (pOSP) secretion into the pig oviduct in the peri-ovulatory period, and effects of previous nutrition

The mechanisms regulating oviduct function were investigated. In Experiment 1, porcine oviductal secretory protein (pOSP) mRNA, and pOSP and insulin-like growth factor (IGF-I) in oviductal flushings, decreased through the peri-ovulatory period. In Experiment 2, higher plasma steroids in oviductal veins, ipsilateral (INT), rather than contralateral (OVX), to the remaining ovary in unilaterally ovariectomized gilts, were associated with higher pOSP in INT oviductal flushings. In Experiment 3, oviduct function was assessed as part of a collaborative study in cyclic gilts. Feed restriction in the late, compared to the early, luteal phase reduced estradiol concentrations in oviductal plasma, pOSP mRNA in oviductal tissue, and IGF-I concentrations and pOSP abundance in oviduct flushings. Previous insulin treatment differentially affected oviduct function. These data provide the first direct evidence for effects of previous feed restriction and insulin treatment on the oviduct environment in the peri-ovulatory period, which may contribute to nutritional effects on embryonic survival

Development of a porcine (Sus scofa) embryo-specific microarray: array annotation and validation

Abstract Background The domestic pig is an important livestock species and there is strong interest in the factors that affect the development of viable embryos and offspring in this species. A limited understanding of the molecular mechanisms involved in early embryonic development has inhibited our ability to fully elucidate these factors. Next generation deep sequencing and microarray technologies are powerful tools for delineation of molecular pathways involved in the developing embryo. Results Here we present the development of a porcine-embryo-specific microarray platform created from a large expressed sequence tag (EST) analysis generated by Roche/454 next-generation sequencing of cDNAs constructed from critical stages of in vivo or in vitro porcine preimplantation embryos. Two cDNA libraries constructed from in vitro and in vivo produced preimplantation porcine embryos were normalized and sequenced using 454 Titanium pyrosequencing technology. Over one million high-quality EST sequences were obtained and used to develop the EMbryogene Porcine Version 1 (EMPV1) microarray composed of 43,795 probes. Based on an initial probe sequence annotation, the EMPV1 features 17,409 protein-coding, 473 pseudogenes, 46 retrotransposed, 2,359 non-coding RNA, 4,121 splice variants in 2,862 genes and a total of 12,324 Novel Transcript Regions (NTR). After re-annotation, the total unique genes increased from 11,961 to 16,281 and 1.9% of them belonged to a large olfactory receptor (OR) gene family. Quality control on the EMPV1 was performed and revealed an even distribution of ten clusters of spiked-in control spots and array to array (dye-swap) correlation was 0.97. Conclusions Using next-generation deep sequencing we have produced a large EST dataset to allow for the selection of probe sequences for the development of the EMPV1 microarray platform. The quality of this embryo-specific array was confirmed with a high-level of reproducibility using current Agilent microarray technology. With more than an estimated 20,000 unique genes represented on the EMPV1, this platform will provide the foundation for future research into the in vivo and in vitro factors that affect the viability of porcine embryos, as well as the effects of these factors on the live offspring that result from these embryos.</p

Individual-, family-, and school-level interventions for preventing multiple risk behaviours relating to alcohol, tobacco and drug use in individuals aged 8 to 25 years

To assess the effects of interventions at the individual, family and school level that aim to target multiple substance use behaviours (two or more from alcohol, tobacco, cannabis, other substance use) for the primary or secondary prevention of substance use and related harms in individuals aged 8 to 25

Characterization of the Altered Gene Expression Profile in Early Porcine Embryos Generated from Parthenogenesis and Somatic Cell Chromatin Transfer

<div><p>The <i>in vitro</i> production of early porcine embryos is of particular scientific and economic interest. In general, embryos produced from <i>in vitro</i> Assisted Reproductive Technologies (ART) manipulations, such as somatic cell chromatin transfer (CT) and parthenogenetic activation (PA), are less developmentally competent than <i>in vivo</i>–derived embryos. The mechanisms underlying the deficiencies of embryos generated from PA and CT have not been completely understood. To characterize the altered genes and gene networks in embryos generated from CT and PA, comparative transcriptomic analyses of <i>in vivo</i> (IVV) expanded blastocysts (XB), IVV hatched blastocyst (HB), PA XB, PA HB, and CT HB were performed using a custom microarray platform enriched for genes expressed during early embryonic development. Differential expressions of 1492 and 103 genes were identified in PA and CT HB, respectively, in comparison with IVV HB. The “eIF2 signalling”, “mitochondrial dysfunction”, “regulation of eIF4 and p70S6K signalling”, “protein ubiquitination”, and “mTOR signalling” pathways were down-regulated in PA HB. Dysregulation of notch signalling–associated genes were observed in both PA and CT HB. TP53 was predicted to be activated in both PA and CT HB, as 136 and 23 regulation targets of TP53 showed significant differential expression in PA and CT HB, respectively, in comparison with IVV HB. In addition, dysregulations of several critical pluripotency, trophoblast development, and implantation-associated genes (<i>NANOG</i>, <i>GATA2</i>, <i>KRT8</i>, <i>LGMN</i>, and <i>DPP4</i>) were observed in PA HB during the blastocyst hatching process. The critical genes that were observed to be dysregulated in CT and PA embryos could be indicative of underlying developmental deficiencies of embryos produced from these technologies.</p></div