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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Livestock Bio-Systems » Research » Research Project #433074

Research Project: Improving Lifetime Productivity in Swine

Location: Livestock Bio-Systems

2019 Annual Report

Objective 1: Improve swine production by identifying factors contributing to prenatal piglet development and survival and postnatal preweaning mortality. Subobjective 1.A: Improve conceptus, postnatal, and preweaning survival by determining early pregnancy factors contributing to variation in fetal and postnatal development. Subobjective 1.B: Increase piglet production by discovering fetal and postnatal development features that are influenced by uterine capacity. Subobjective 1.C: Determine the influence of placental membrane transporters on placental and fetal development. Objective 2: Increase productivity and longevity of replacement gilts by identifying and defining physiological and environmental factors underlying developmental and reproductive processes. Subobjective 2.A: Improve strategies for selecting gilts by defining environmental, physiological, and metabolic factors responsible for variation in growth and reproductive efficiency. Subobjective 2.B: Reduce failure of gilt retention through discovery of gene pathways and their interaction with physiological and environmental factors affecting the phenotypic expression of pubertal traits. Objective 3: Enhance sow performance and retention within the breeding herd by identifying physiological and environmental features at critical periods throughout life that contribute to production and longevity. Subobjective 3.A: Identify behavioral and environmental factors during gestation, lactation, or post-weaning periods to develop feeding strategies that improve sow reproductive performance and longevity. Subobjective 3.B: Discover factors (microbiome profiles, metabolites, transcripts, proteins, and/or genes) within tissues or biofluids from female breeding stock for use in genomic, metabolomic, or microbiome studies to improve reproductive efficiency, piglet production, and sow longevity.

Maximizing lifetime productivity of swine is essential to meet the ARS Grand Challenge of a 20% increase in production and a 20% reduction in environmental impact by 2025 and is a high priority research initiative of the pork industry. Lifetime productivity of swine is an extremely complex trait and our understanding of the biological mechanisms that underlie the trait or its component traits is limited. Increasing our knowledge and basic understanding of development, growth, and maintenance at all levels of swine production will impact lifetime productivity. The overarching goal is to discover physiological, metabolic, and environmental factors affecting fetal survival, piglet growth, reproductive development, and sow productivity and longevity. This will be accomplished by combining transcriptomics, metabolomics, microbiomics and other molecular biology techniques with genetic and physiological studies at the farm level. Our first objective will focus on conceptus through neonate to produce more consistent-sized, healthy piglets, subsequently reducing pre-weaning mortality and improving growth rates. Secondly, we will identify factors that contribute to young females that have greater success entering and staying in the breeding herd. Our final objective will investigate environmental and energy dynamics of mature females relating these to production and longevity. The tools and strategies developed from this project will be used to improve pork production efficiency. Maximizing lifetime productivity of swine will enhance the welfare and well-being by minimizing fetal and neonatal death, and reducing unnecessary culling of gilts and sows. Application of these results will increase the economic competitiveness of U.S. pork producers.

Progress Report
Substantial progress has been made toward all three objectives and their subobjectives, all of which fall under National Program 101, Component 1: Increasing Production and Production Efficiencies while Enhancing Animal Well-Being across Diverse Food Animal Production Systems, Problem Statement 1B, Improving Reproductive Efficiency; and Component 2: Understanding, Improving, and Effectively Using Animal Genetic and Genomic Resources, Problem Statement 2A, Develop Bioinformatic and other Required Capacities for Research in Genomics and Metagenomics and Problem Statement 2B, Characterize Functional Genomic Pathways and their Interactions. Under Subobjective 1A, we have begun to sample sows bred with Landrace sires and continue to evaluate the influence of early gestation progesterone levels and subsequent farrow results. We lost 5 weeks of sampling due to the government shutdown between December 2018 and January 2019 that will extend the sampling by two months. As of July 22, 2019, we have collected plasma samples from 1500 dams, measured early gestation progesterone in 1200 dams and compared farrowing results in 500 dams. Within Subobjective 2B, we have continued to evaluate limited number of excess bred gilts (total of 9 as of July 22, 2019) to evaluate ovulation rate and uterine capacity in early parity commercial females. The evaluation of ovulation rate and uterine capacity from late parity females from weaning potential and productivity quadrants sow will be initiated at the completion of the large progesterone evaluation project (1A) in mid-FY2020. Under Subobjective 2A, phenotypic data on gilts that move through the feed efficiency barn continues to be collected as described. Reproductive data is being collected and records are added to the data base. Blood analysis is on hold until we identify the most informative animals (most phenotypes) as described in the project plan. Pubertal phenotypic data collected also support work within Subobjective 2B., in which tissue for RNAseq analysis has been collected from both populations (Yorkshire and Landrace sired females). RNA-seq libraries are being constructed from medial basal hypothalamus and amygdale tissue. RNA-seq on hippocampus and olfactory bulb has been completed. Analysis on those results are underway. Under Subobjective 3A, we have acquired the equipment to monitor temperature, relative humidity, and lumens of light within the gestation facilities. However we are still working through some issues with data collection from the feeding systems. We will be starting the project about nine to twelve months behind schedule, as we develop other means of collecting the feed station data. If we reduce our data collection to two or two and half years, instead of the full three years, several of the females will have multiple parity information, at which time we will determine if we need to extend the collection period in order to have suitable data for analyses. Within Subobjective 3B, progress has been made towards the microbiome analysis of milk from parity 1 through parity 4 sows that is being actively performed in association with collaborators. Additionally, metabolite profiling of plasma samples from post-farrowing collections are currently being submitted for ultra performance liquid chromatography-mass spectrometry (UPLC-MS) and data analysis. Progress has also been made in refining protocols to complete metabolite profiling from milk samples using UPLC-MS.

1. Compounds within the uterine environment are unique to the type of elongating embryos present. In the pig, deficiencies in embryo elongation contribute to approximately 20% of the embryonic loss, and have a direct influence on within-litter birth weight variation, which influences preweaning piglet survival and long term growth and development. Alterations in the signaling of critical molecular factors within the uterus results in deficiencies in embryo elongation associated with delayed embryonic elongation and embryonic loss. To identify factors that initiate and progress embryos through early stages of elongation, ARS scientists at Clay Center, Nebraska, in collaboration with scientists from University of Nebraska and Colorado State University, performed metabolomics analyses of uterine milieu from early pregnancies containing either uniform or diverse populations of embryos as they transition between the initiation and early stages of elongation. Some of these metabolites were greater in the environment of early spherical embryos such as uric acid, tryptophan, and tyrosine. Other metabolites were greater in the environment of later stage embryos such as serine, phenylalanine, and phosphoric acid. These novel data illustrate several putative metabolites that change within the uterine milieu as porcine conceptuses transition between spherical, ovoid, and tubular conceptuses. Variation of these metabolites in unique patterns provide possible molecular signals necessary to initiate and progress embryos through early stages of elongation. These data provide not only basic understanding of early porcine embryo activity, but provide possible interventions that can improve embryonic survival and litter size and uniformity.

2. Blood vessel size and dilation of vasculature supplying the boar testes are heritable. The vasculature outside of each testis, known as the pampiniform plexus, provides blood to the testis, and acts as a countercurrent heat exchange to maintain appropriate testicular temperature. When these vessels are abnormally dilated or contain lesions, a condition known as varicocele interferes with blood flow and heat exchange. This condition is known in humans and contributes greatly to infertility, however in swine, less is known about this condition. An ARS scientist at Clay Center, Nebraska, along with University of Nebraska researchers, using ultrasonography, measured the right and left pampiniform plexus vessel area and determined the presence of varicocele in a large population of young boars. They further derived the genetic heritability of vessel area and varicocele. Pampiniform plexus vessel area was highly heritable while presence of varicocele was moderately heritable. These data suggest that boars could be selected for both vessel area and presence of varicocele, thereby improving fertility characteristics of breeding boars, which would lead to improved economic and animal production efficiencies for pork producers.

3. Season of semen collection and season of breeding influence the activity of genes in placenta and fetal liver. In modern swine facilities, regulated environments are maintained, however subtle changes still exist due to season of the year causing a consistent and chronic transient reductions in reproductive performance primarily during the summer months. External factors; such as season of year; influence gene expression, and are referred to as epigenetic effects. ARS scientists at Clay Center, Nebraska, along with University of Wisconsin researchers, determined the epigenetic influence of; season of semen collection, storage of semen, and breeding season on epigenetic activity and expression of epigenetic responsive genes in the placenta and fetal livers at 45 days pregnancy. Activity and expression of responsive genes were changed due to season of semen collection or season of breeding. These results provide basic novel evidence that seasonality from male and female contributions on gene activity in placenta and fetal livers still persists, affecting tissue development and growth. Future research using other epigenetic influencers; such as diet, temperature, and light exposure; may act to counterbalance negative seasonal effects on summer matings or on semen quality thereby improving reproductive efficiency for pork producers.

Review Publications
Gruhot, T.R., Rempel, L.A., Spangler, M.L., Stephen, K.D., Mote, B.E. 2019. The heritability of pampiniform plexus vessel size and varicocele in boars. Reproduction of Domestic Animals. 54(2):270-274.
Rempel, L.A., Krautkramer, M.M., Parrish, J.J., Miles, J.R. 2019. Impact of seasonality, storage of semen, and sperm head-shape on whole tissue methylation and expression of methylation responsive candidate genes in swine placenta and fetal livers from summer and winter breedings. Molecular Reproduction and Development. 86(4):465-475.
George, A.F., Ho, T., Prasad, N., Keel, B.N., Miles, J.R., Vallet, J.L., Bartol, F.F., Bagnell, C.A. 2019. Neonatal lactocrine deficiency affects the adult porcine endometrial transcriptome at pregnancy day 13. Biology of Reproduction. 100(1):71-85.
Lindholm-Perry, A.K., Kuehn, L.A., McDaneld, T.G., Miles, J.R., Workman, A.M., Chitko-McKown, C.G., Keele, J.W. 2018. Complete blood count data and leukocyte expression of cytokine genes and cytokine receptor genes associated with bovine respiratory disease in calves. BMC Research Notes. 11:786.
Tenley, S.C., Spuri Gomes, R., Rosasco, S.L., Northrop, E.J., Rich, J.J., McNeel, A.K., Summers, A.F., Miles, J.R., Chase, Jr., C.C., Lents, C.A., Perry, G.A., Wood, J.R., Cupp, A.S., Cushman, R.A. 2019. Maternal age influences the number of primordial follicles in the ovaries of yearling Angus heifers. Animal Reproduction Science. 200:105-112.
Lents, C.A., Freking, B.A. 2019. Intrauterine position and adjacent fetal sex affects fetal and placental growth throughout gestation, but not embryonic viability, in pigs selected for component traits of litter size. Animal Reproduction Science. 209:106139.