The number of teats is a reproductive-related trait of great economic relevance as it affects the mothering ability of the sows and thus the number of properly weaned piglets. Moreover, genetic improvement of this trait is fundamental to parallelly help the selection for increased litter size. We present the results of single-marker and haplotypes-based genome-wide association studies for the number of teats in two large cohorts of heavy pig breeds (Italian Large White and Italian Landrace) including 3990 animals genotyped with the 70K GGP Porcine BeadChip and other 1927 animals genotyped with the Illumina PorcineSNP60 BeadChip. In the Italian Large White population, genome scans identified three genome regions (SSC7, SSC10, and SSC12) that confirmed the involvement of the VRTN gene (as we previously reported) and highlighted additional loci known to affect teat counts, including the FRMD4A and HOXB1 gene regions. A different picture emerged in the Italian Landrace population, with a total of 12 genome regions in eight chromosomes (SSC3, SSC6, SSC8, SSC11, SSC13, SSC14, SSC15, and SSC16) mainly detected via the haplotype-based genome scan. The most relevant QTL was close to the ARL4C gene on SSC15. Markers in the VRTN gene region were not significant in the Italian Landrace breed. The use of both single-marker and haplotype-based genome-wide association analyses can be helpful to exploit and dissect the genome of the pigs of different populations. Overall, the obtained results supported the polygenic nature of the investigated trait and better elucidated its genetic architecture in Italian heavy pigs.

中文翻译：

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两种重型猪品种乳头数量的基于单倍型和单倍型的全基因组关联研究

乳头数量是一种与生殖相关的性状，具有重要的经济意义，因为它会影响母猪的母性能力，从而影响适当断奶的仔猪数量。此外，该性状的遗传改良对于同时帮助选择增加的窝产仔数至关重要。我们展示了两个大型重猪品种（意大利大白猪和意大利长白猪）中乳头数量的单标记和基于单倍型的全基因组关联研究的结果，包括 3990 只用 70K GGP Porcine BeadChip 和其他基因分型的动物。 1927 只动物使用 Illumina PorcineSNP60 BeadChip 进行基因分型。在意大利大白人群体中，基因组扫描确定了三个基因组区域（SSC7、SSC10 和 SSC12），证实了VRTN的参与基因（正如我们之前报道的）并突出显示了已知影响乳头计数的其他基因座，包括FRMD4A和HOXB1基因区域。在意大利长白种种群中出现了不同的情况，主要通过基于单倍型的基因组扫描检测到 8 条染色体（SSC3、SSC6、SSC8、SSC11、SSC13、SSC14、SSC15 和 SSC16）中的 12 个基因组区域。最相关的 QTL 接近SSC15上的ARL4C基因。VRTN中的标记基因区域在意大利长白品种中不显着。使用单标记和基于单体型的全基因组关联分析有助于开发和剖析不同种群猪的基因组。总体而言，获得的结果支持所研究性状的多基因性质，并更好地阐明了其在意大利重型猪中的遗传结构。