|WIJESENA, H - University Of Nebraska|
|REITHOVEN, J-J - University Of Nebraska|
|TRENHAILE-GRANNEMANN, M - University Of Nebraska|
|THORSON, J - University Of Nebraska|
|MILLER, P - University Of Nebraska|
|SPANGLER, M - University Of Nebraska|
|KACHMAN, S - University Of Nebraska|
|CIOBANU, D - University Of Nebraska|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2017
Publication Date: 9/14/2017
Publication URL: https://handle.nal.usda.gov/10113/5832852
Citation: Wijesena, H.R., Lents, C.A., Reithoven, J.-J., Trenhaile-Grannemann, M.D., Thorson, J.F., Keel, B.N., Miller, P.S., Spangler, M.L., Kachman, S.D., Ciobanu, D.C. 2017. GENOMICS SYMPOSIUM: Using genomic approaches to uncover sources of variation in age at puberty and reproductive longevity in sows. Journal of Animal Science. 95:4196-4205. https://doi.org/10.2527/jas2016.1334.
Interpretive Summary: Limitations in reproductive longevity of sows are a major constraint in pork production. Selection to improve reproductive longevity is challenging because the phenotype is expressed late in life and has a low genetic heritability. In order to overcome this challenge, scientists at the University of Nebraska, Lincoln and ARS scientists at Clay Center, Nebraska determined the effects of genetics and nutrition on reproductive longevity of sows. Scientists developed female pigs called gilts on two different diets and used massive DNA sequencing and DNA genotyping on hundreds of animals to uncover genetic markers. They discovered several regions of the DNA that affect age at puberty and reproductive longevity of pigs. Scientists used high-throughput sequencing of gene transcripts to determine what genes are expressed in reproductive tissues of gilts. They discovered many genes that were expressed differently in gilts fed the two different diets, and in gilts that reached puberty earlier versus later. They found that gilts which reach puberty earlier have greater reproductive longevity. Scientists will use these data to test how these genetic markers can be used for selecting and improving reproductive development and longevity of sows. The research results will be integrated into university extension programs to facilitate the adoption of research findings by the pork industry. By improving reproductive longevity, scientists can reduce the number of sows that are kept for breeding and that are culled thereby improving efficiency of pork production. This is necessary to feed a growing world population. The added benefit is that animal well-being will be improved and the impact of swine production on natural resources will be reduced.
Technical Abstract: Genetic variants associated with traits such as age at puberty and litter size could provide insight into the underlying genetic sources of variation impacting sow reproductive longevity and productivity. Genomewide characterization and gene expression profiling were used using gilts from the University of Nebraska–Lincoln swine resource population (n = 1,644) to identify genetic variants associated with age at puberty and litter size traits. From all reproductive traits studied, the largest fraction of phenotypic variation explained by the Porcine SNP60 BeadArray was for age at puberty (27.3%). In an evaluation data set, the predictive ability of all SNP from high-ranked 1-Mb windows (1 to 50%), based on genetic variance explained in training, was greater (12.3 to 36.8%) compared with the most informative SNP from these windows (6.5 to 23.7%). In the integrated data set (n = 1,644), the top 1% of the 1-Mb windows explained 6.7% of the genetic variation of age at puberty. One of the high-ranked windows detected (SSC2, 12–12.9 Mb) showed pleiotropic features, affecting both age at puberty and litter size traits. The RNA sequencing of the hypothalami arcuate nucleus uncovered 17 differentially expressed genes (adjusted P < 0.05) between gilts that became pubertal early (<155 d of age) and late (>180 d of age). Twelve of the differentially expressed genes are upregulated in the late pubertal gilts. One of these genes is involved in energy homeostasis (FFAR2), a function in which the arcuate nucleus plays an important contribution, linking nutrition with reproductive development. Energy restriction during the gilt development period delayed age at puberty by 7 d but increased the probability of a sow to produce up to 3 parities (P < 0.05). Identification of pleotropic functional polymorphisms may improve accuracy of genomic prediction while facilitating a reduction in sow replacement rates and addressing welfare concerns.