Location: Livestock Bio-Systems
2023 Annual Report
Objectives
Objective 1. Improve postnatal survival of preweaning piglets by identifying factors that contribute to within-litter variations on piglet growth and development.
Sub-objective 1.A: Determine the influence of ovarian responses (OR and serum P4 levels) during early gestation on within-litter variation in embryo elongation and uterine environmental responses in young females (Exp. 1) and multi-parous sows (Exp. 2).
Sub-objective 1.B: Evaluate the influence of regulatory factors (i.e., miRNAs) and nutrient transfer (i.e., metabolites) from maternal to fetal plasma across the placenta on divergent-sized fetal growth and within-litter variation during late gestation using a global approach (i.e., RNA-seq and non-targeted metabolomics, respectively).
Objective 2. Discover nutritional and environmental influences on gilt development and productivity to minimize reproductive failure of replacement gilts.
Sub-objective 2.A: Improve gilt development by understanding how growth relates to prebreeding anestrus.
Sub-objective 2.B: Minimize pubertal failure in gilts by identifying mechanisms in the anterior pituitary gland that are mediating the effects of nutrient balance on secretion of gonadotropin hormones necessary for initiation and maintenance of reproductive cycles.
Sub-objective 2.C: Improve neonatal management of replacement gilts by identifying how colostrum intake impacts early ovarian development.
Objective 3. Identify and evaluate biological predictors of sow performance and longevity within the breeding herd.
Sub-objective 3.A: Identify plasma biomarkers and blood transcript profiles from young pre-breeding females and associate those profiles with their subsequent breeding herd longevity.
Sub-objective 3.B: Evaluate USMARC swine population for effects of seasonal climate upon production parameters over the past decade.
Sub-objective 3.C: Generate hypomethylated, hypermethylated, or control pregnancies during summer or winter months to determine epigenetic impact upon placental, fetal, and piglet production.
Objective 4. Utilize and develop precision management technologies to improve preweaning piglet survival, gilt development, and sow longevity and increase efficiency of pork production.
Sub-objective 4.A.: Utilize ESF data to develop prediction models for gilt fertility (e.g., behavioral estrus) and sow welfare during gestation (e.g., abortion/miscarriage, lameness, appropriate body weight).
Approach
Pork is the most consumed meat animal product globally. Improving lifetime efficiency of swine is critical to support an increasing global population. Improved lifetime efficiency will provide a high-quality source of protein while reducing the impact of swine production on the environment and ensuring the social welfare of animals. Lifetime efficiency is a complex trait that is influenced by genetic, environment, and management components. The comprehensive goal for this project is to further our understanding of these traits using physiology-, biology-, and technology-based approaches to provide improvements for fetal and neonatal health, gilt development, and sow longevity. We will accomplish this goal utilizing independently, and in combination, transcriptomics, metabolomics, proteomics, environmental data, and automated precision measurements (Figure 1). Within objective 1, we will investigate molecular pathways and signals that improve production of consistently sized piglets initiated shortly after conception. Objective 2 will delve into the influence nutrition has on the young female and the impact upon neuroendocrine gene expression as the gilt transitions into the active state of reproduction. Identifying biological markers that can assist in selecting females with longevity in the breeding system and investigating climate and therapeutics to assist with stayability are the central themes of Objective 3. In the fourth objective, feeding behavior and activity measurements of young gilts and gestating females will be collated and activity patterns will be generated to predict reproductive success or failure. The projects designed herein will clarify and contribute to the existing complex knowledge gap of swine productive life. Application of these studies will result in breeding females that are consistently well adapted, produce large litters of uniform piglets and remain fertile and healthy in the swine herd increasing production efficiency, improve economic competitiveness of U.S. pork producers, and contribute to basic understanding of biological and environmental influences upon swine production.
Progress Report
Significant progress has been made to address the four objectives for the project, Improving Lifetime Productivity in Swine using Systems Biology and Precision Management Approaches. For Objective 1, progress has been made utilizing embryonic samples collected from early gestation pregnant gilts to evaluate specific factors that regulate the initiation of conceptus elongation and potentially contribute to within-litter variation. Scientists characterized expression levels for glycerophospholipid and sphingolipid enzymes from the embryonic disc and trophectoderm within the embryo during the initiation of elongation. These results illustrate that gene regulation of glycerophospholipid enzymes influence all cell types of the early embryo, whereas sphingolipid enzymes are primarily regulated with the trophectoderm and illustrate the importance of these lipids to drive the initiation of porcine embryo elongation. In support of these findings, another study utilizing our previously developed culture system identified many unique compounds secreted into the culture media from embryos undergoing initiation of elongation. There were many glycerophospholipid and sphingolipid metabolites among these compounds that increased as embryos underwent initiation of elongation, which further highlights the importance of these lipids on initiation of embryo elongation.
Within Objective 2, body weights for 14,000 gilts during development were analyzed. Relationships between body weight and pubertal phenotypes were estimated. Methods were developed to upload body weight data from electronic sow feeders (ESF). Database tables were modified and data from 1,400 gilts were recorded within the current year.
In support of Objective 3, sows that have fully transitioned through the breeding herd (approximately 800 days of age) were identified by their lifetime potential and productivity of piglets raised. Previously collected blood samples (prior to entry into the breeding herd, approximately 170 days of age) from these animals are currently being processed for differentially expressed genes that could be used as early life biomarkers to predict female lifetime productivity potential. Archived and current data are being collated to investigate the influence of season during breeding and gestation on mothering ability and performance in the farrowing system. The final portion of environmental data and feeding activity in the gestation barn was completed in June and collating of this data along with farrowing data has been initiated.
To support the efforts of Objective 4, the use of ESF in the gilt development and gestation barns allows feeding activity/behavior and body weights to be recorded daily, which are then transferred to the relational database. In addition, animal care takers are recording physiological events to the database, such as estrus activity from the gilts, health and welfare events from gilts and sows, farrowing traits, and culling/removal events.
Scientists are actively involved with three externally funded projects all of which lend support to the project plan. In collaboration with academic peers, early-stage embryos are being generated and harvested for extracellular vesicle evaluation focusing on within-litter birthweight variation and preweaning survival in support of Objective 1. A second externally funded project involves the investigation of in utero heat stress on boar fertility with university researchers. Boar fertility indirectly relates to Objectives 1, 2, and 3. A final externally funded project between ARS and academic scientists is being initiated in which piglets will be treated with antibiotics or an essential oil then monitored for growth, health, and performance. Gilts that remain within the herd will be observed for fertility and lifetime reproductive performance in line with Objectives 2 and 3. A collaborative project among researchers at Clay Center, Nebraska, and academic colleagues in Nebraska, Michigan, and California, has investigated the use of geophones (e.g., seismic sensors) on farrowing stalls, accelerometers (movement in the X, Y, and Z planes) on the smallest, average, and largest-size piglets in select litters, and video imaging of farrowing and litter activities during early piglet life. The geophones successfully recorded individual sow heart rates prior to farrowing and general activity during farrowing, which could lead to precision technologies to alert personnel of distress prior to or difficulty during farrowing in support of Objective 4. In support of Objective 1, the accelerometer data and video data of recorded piglet activities are being correlated with pre-weaning growth and survival.
Accomplishments
1. New genetic markers identified that can improve reproduction in sows. Selecting optimally developed replacement females is challenging because reproductive traits are lowly heritable and expressed late in life. Age at puberty is the earliest indicator of future reproductive success of gilts, but genetic selection for early onset of puberty is limited due to lack of molecular genetic predictors. ARS scientists at Clay Center, Nebraska, conducted a large-scale genome-wide association study to identify genomic regions associated with variation in age at puberty in gilts. They identified both previously known and new novel genomic associations. Candidate genes, identified within these genomic regions, were found to be involved in hormone secretion and ovarian function. These data provide important new markers for use in swine breeding programs to select replacement gilts and improve sow longevity and productivity for United States Pork Producers.
2. Lab approach to study pregnancy losses in pigs. In the pig, deficiencies in embryo elongation contribute to embryonic loss and reduced pregnancy outcomes. The exact mechanisms regulating elongation are poorly understood due to the complexity of the uterine environment and difficulty to replicate this process in a laboratory environment. ARS scientists at Clay Center, Nebraska, in collaboration with scientists from the University of Nebraska-Lincoln, previously developed a culture system using a three-dimensional matrix that facilitates the initiation of porcine embryo elongation, enabling real-time study of elongation in a controlled laboratory environment. The objective of the current study was to examine differences among the secretions from individual embryos either initiating or not initiating elongation. This study identified changes in lipid compounds from embryos that were initiating elongation from those embryos not elongating. The results from this work can translate into possible lipid supplementation to pregnant females creating a favorable uterine environment that better supports elongation and establishment of embryos. Producers can benefit from potentially using a simple supplement to improve litter size and consistency of piglets.
3. Gene editing to develop castration free pigs. Male piglets destined for pork production are castrated to prevent development of aggressive male behaviors that increase the risk of injuries to other pigs and workers, and to meet consumer expectations for pork quality. Gene editing technologies provide an opportunity to develop alternatives to castration. Researchers in collaboration with ARS scientists at Clay Center, Nebraska, edited a key gene in the reproductive system called KISS1. Scientists found that editing the KISS1 gene kept testes of male pigs from developing, but all other aspects of pig development were normal. These results demonstrate the potential to use gene editing for genomic based alternatives to castration that will lead to improved animal welfare for market pigs.
Review Publications
Walsh, S.C., Miles, J.R., Broeckling, C.D., Rempel, L.A., Wright-Johnson, E.C., Pannier, A.K. 2023. Secreted metabolome of porcine blastocysts encapsulated within in vitro 3D alginate hydrogel culture systems undergoing morphological changes provides insights into specific mechanisms involved in the initiation of porcine conceptus elongation. Journal of Reproduction, Fertility and Development. 35(5):375-394. https://doi.org/10.1071/RD22210.
Florez, J.M., Martins, K., Solin, S., Bostrom, J.R., Rodriguez-Villamil, P., Ongaratto, F., Larson, S.A., Ganbaatar, U., Coutts, A.W., Kern, D., Murphy, T.W., Kim, E., Carlson, D.F., Huisman, A., Sonstegard, T.S., Lents, C.A. 2023. CRISPR/Cas9-editing of KISS1 to generate pigs with hypogonadotropic hypogonadism as a castration free trait. Frontiers in Genetics. 13. Article 1078991. https://doi.org/10.3389/fgene.2022.1078991.
Wijesena, H.R., Nonneman, D.J., Snelling, W.M., Rohrer, G.A., Keel, B.N., Lents, C.A. 2023. gBLUP-GWAS identifies candidate genes, signaling pathways, and putative functional polymorphisms for age at puberty in gilts. Journal of Animal Science. Article skad063. https://doi.org/10.1093/jas/skad063.
White, B.R., Cederberg, R.A., Elsken, D.H., Ross, C.E., Lents, C.A., Desaulniers, A.T. 2023. Role of gonadotropin-releasing hormone-II and its receptor in swine reproduction. Molecular Reproduction and Development. 90(7):469-479. https://doi.org/10.1002/mrd.23662.
