Project : USDA ARS

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

2021 Annual Report

Objectives
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.

Approach
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
Significant progress has been made to address the three objectives: prenatal development and survival and postnatal preweaning survivability, productivity and longevity of gilts, and sow performance and retention. Within Objective 1, evaluation and sampling of excess bred females for ovulation rate and uterine capacity continues. To date, ARS researchers have collected information on 36 of the planned 75 litters. These data support the efforts investigating the early conceptus uniformity, which contributes to placental development and function and within-litter birthweight variation. Analyses of progesterone from early pregnancy females has been completed in support of Objective 1. Embryo elongation and membrane vesicle exosome work continues in collaboration with university partners under an existing and a newly funded Agricultural Food Research Initiative/National Institute of Food and Agriculture proposal. Objective 2 was supported by internal and multi-institution projects contributing to the understanding of pubertal development in gilts and stayability of sows in the breeding herd. Assessment of gilt development and growth continues as young females transition through the feed efficiency facility at Clay Center, Nebraska. Piglet survival and colostrum consumption greatly influence gilt development at the earliest phases of neonatal life. Within Objective 2, genetic analyses and differential gene expression of pubertal traits and sow longevity are actively being addressed and supported by post-doctoral efforts. Transcriptomic short-read and long-read RNA sequence for olfactory epithelium, hypothalamus, and pituitary were provided to Iowa State University in contribution to the Functional Annotation of the Porcine Genome project as part of Objective 2. In support of Objective 3, studies are being conducted to bolster the understanding of physiological events and environmental factors that impact sow longevity in the breeding herd. Environmental data, feeding activity, and body weights are actively being collected within the gestation pens and will be correlated to subsequent farrowing activity, including sow behavior and piglet production and performance. Plasma samples from post-4th parity dams were evaluated for compounds using high performance liquid chromatography-mass spectrometry and analyzed. Initial review of the results, indicate a compound with apoptotic inhibitor activity is unique to sows with the greatest litter sizes and weaning performance over the course of their productive lifetime. Findings from microbiome evaluation of early and mid-lactation milk from dams of first through fourth parity will be presented at scientific meetings in support of Objective 3. Metabolomic projects are currently being performed using various tissue samples from post-4th parity dams of varying lifetime piglet production categories. In addition, RNA-sequencing (RNA-Seq) gene expression matrices for multiple reproductive tissues (olfactory epithelium, medial basal hypothalamus, anterior pituitary, ovary, amygdala, and hippocampus) in pigs were provided to the University of Edinburgh in contribution to the Pig genotype-tissue expression (Pig GTEx) consortium. Tissues analyzed were primarily samples from the current project plan. The goal is to provide an atlas of tissue-specific gene expression and regulation in pigs. The RNA- Seq we provided to the University of Edinburgh enables validation for a transcriptome wide association study that they are conducting using the Pig GTEx data. This new approach is based on prior knowledge of the distribution of gene expression of individual genes within a given tissue. In support of Functional Annotation of Animal Genomes (FAANG) consortium, several RNA-Seq and Isoform-seq data collated from tissues collected and analyzed within the current project plan, were submitted for improved reference genome assembly and phenotypic datasets. Maximizing functional annotation in healthy adult porcine tissues relevant to phenotypes is important for genetic improvement.

Accomplishments
1. Methods to improve piglet survival. Newborn piglets have low levels of blood oxygen and wet skin, which predisposes them to mortality from loss of body heat and weakness. ARS scientists at Clay Center, Nebraska, in collaboration with the University of Illinois studied how to minimize the loss of body heat from newborn piglets and how providing supplemental oxygen to newborn pigs affects their ability to suckle. Researchers found that both drying the newborn piglets and warming them in a box for 30 minutes after birth reduced their loss of body heat and improved survival of the smallest piglets, but supplemental oxygen was not beneficial. Losses due to piglet mortality prior to weaning are estimated at $1.25 billion annually in the U.S. and increasing the number of weaned pigs per litter by 0.5 would yield over $300 million in annual economic benefit to the swine industry.

2. Genetic variants linked with sexual maturity in pigs. About one-third of sow culls are due to reproductive failure and most of these removals are younger females. Young female pigs that reach sexual maturity earlier tend to stay in the herd longer and be more productive. ARS researchers at Clay Center, Nebraska, investigated genetic variants in six candidate genes for the trait, age at puberty, within previously identified areas of interest in the swine genome. Several variants were identified within the swine aryl hydrocarbon receptor gene, which can be used to identify females with favorable sexual maturation attributes. Reducing culling of young female pigs by 10% equates to a favorable benefit-to-cost value of nearly $172 million within the industry.

3. Reproductive failure is the leading reason breeding female pigs (gilts) are culled. ARS scientists at Clay Center, Nebraska, examined how cells in the brain are involved in controlling reproduction in gilts. They found that certain cells express two types of proteins, called kisspeptin and neurokinin B, and these cells are uniquely organized in the pig brain to control secretion of reproductive hormones. This is the first report of localization of these proteins in pigs. This foundational knowledge will be critical for developing new strategies and technologies to better manage reproduction and increase fertility in gilts. In the U.S., approximately 2.4 million young breeding females (40% of total young females retained for breeding) are culled annually due to reproductive failure at a loss on net return on investment of $50 million dollars to swine producers.

U.S. DEPARTMENT OF AGRICULTURE

Livestock Bio-Systems: Clay Center, NE