Abstract
BackgroundPiglet birth weight variability, a trait also known as the within-litter homogeneity of birth weight, reflects the sow’s prolificacy, because it is positively genetically correlated with preweaning mortality but negatively correlated with the mean growth of piglets during sucking. In addition, the maternal additive genetic variance and heritability has been found exist for this trait, thus, reduction in the variability of piglet birth weight to improve the sow prolificacy is possible by selective breeding.ResultsWe performed a genome wide association study (GWAS) in 82 sows with extreme standard deviation of birth weights within the first parity to identify significant SNPs, and finally 266 genome-wide significant SNPs (p < 0.01) were identified. These SNPs were mainly enriched on chromosome 7, 1, 13, 14, 15 and 18. We further scanned genes of the top 50 SNPs with the lowest p values and found some genes involved in plasma glucose homeostasis (GLP1R) and lipid metabolism as well as maternal-fetal lipid transport (AACS, APOB, OSBPL10 and LRP1B) which may contribute to the birth weight variability trait.ConclusionsBirth weight variability trait has a low heritability. It is not easy to get significant signal by GWAS using small sample size. Herein, we identified some candidate chromosome regions especially chromosome 7 and suggested five genes which may provide some information for the further study.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-015-0309-6) contains supplementary material, which is available to authorized users.
Highlights
Piglet birth weight variability, a trait known as the within-litter homogeneity of birth weight, reflects the sow’s prolificacy, because it is positively genetically correlated with preweaning mortality but negatively correlated with the mean growth of piglets during sucking
We performed a Genome wide association study (GWAS) in 82 sows (39 with low variability and 43 with high variability) by using the Illumina porcine 60K single nucleotide polymorphisms (SNPs) chip to identify significant SNPs associated with the birth weight variability at a genome level, identified the major candidate genes associated with this trait
For the 266 significant SNPs, 17 SNPs have not been mapped to any chromosome, and the other 249 SNPs were mainly enriched on chromosome 1, 7, 13, 14, 15 and 18 (Fig. 1)
Summary
A trait known as the within-litter homogeneity of birth weight, reflects the sow’s prolificacy, because it is positively genetically correlated with preweaning mortality but negatively correlated with the mean growth of piglets during sucking. The maternal additive genetic variance and heritability has been found exist for this trait, reduction in the variability of piglet birth weight to improve the sow prolificacy is possible by selective breeding. Litter size at birth has been considered as the most important index for evaluating sow productivity and great genetic improvement has been successfully obtained for this trait in most of commercial pig breeds [1,2,3,4]. We performed a GWAS in 82 sows (39 with low variability and 43 with high variability) by using the Illumina porcine 60K SNP chip to identify significant SNPs associated with the birth weight variability at a genome level, identified the major candidate genes associated with this trait. The filtered SNP loci may be used as a preliminary foundation for further selective breeding
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