One of the biggest challenges in the swine industry is to increase female reproductive efficiency. Recently, vulva score categories (VSC), assessed prior to puberty, has been proposed as an indicator trait of efficient reproductive performance in sows. The objective of this study was to validate the use of VSC as an indicator trait for reproductive performance, and to perform genetic and genomic analyses for VSC. The phenotypic relationship of VSC, using a three-point scale: small (VSC-S), medium (VSC-M), and large (VSC-L), on reproductive performance was evaluated on three farms. VSC was measured at 15 weeks of age, for farms 1 and 2, and at 14 weeks of age for farm 3 on 3981 Yorkshire gilts, in which 1083 had genotypes (~ 50 K SNPs). Genetic parameters for VSC with reproductive traits were estimated using ssGBLUP. A Genome-wide association study (GWAS) for VSC was performed using BayesB. For the phenotypic analysis of VSC across datasets, differences in performance were identified there was a significant effect (P ≤ 0.05) for the interaction between Farm and VSC for total number dead (TND), and a trend (P < 0.10) for total number born (TNB). There were significant (P ≤ 0.05) pre-defined contrasts of VSC-S versus VSC-M + L on TNB, number born alive (NBA), TND, number of stillborn (NSB), and number of mummies (MUM). Heritability estimates for VSC as a categorical trait (VSCc) and a quantitative trait (VSCq) were 0.40 ± 0.02 and 0.83 ± 0.02, respectively, for across farm, 0.13 ± 0.07 and 0.20 ± 0.10, respectively, for Farm1, 0.07 ± 0.07 and 0.09 ± 0.09, respectively, for Farm2, and 0.20 ± 0.03 and 0.34 ± 0.05, respectively, for Farm3. For across farms, favorable genetic correlations estimates were found for TNB (0.28 ± 0.19) and NBA (0.26 ± 0.17). Within farms, moderate genetic correlations between VSC with reproductive traits were found for TNB (0.61 ± 0.47) and MUM (0.69 ± 0.47) for farm 1, for number of services until first farrow (NS; 0.69 ± 0.38) and unique service with successful first farrow (SFS; − 0.71 ± 0.38) for farm 3. Multiple genomic regions associated with VSCc were identified. Of these, a QTL located on chromosome 3 at 33–34 Mb accounted for about 7.1% of the genetic variance for VSCc and VSCq. This region harbors the gene PRM1 that has been associated with early embryonic development in pigs. The results support potential of VSC for improved reproductive efficiency on first-parity performance, but the results might depend on the interaction between environmental factors and VSC, as well as potentially additive genetics.

中文翻译：

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初产母猪外阴评分类别与生殖性能之间的表型和基因组关系

养猪业的最大挑战之一是提高女性生殖效率。近来，已提出在青春期之前评估的外阴得分类别（VSC）作为母猪有效生殖性能的指标特征。这项研究的目的是验证使用VSC作为生殖性能的指标性状，并对VSC进行遗传和基因组分析。在三个农场上，使用三点量表（小（VSC-S），中（VSC-M）和大（VSC-L））对VSC的表型关系进行了评估。在3981个约克郡后备母猪上，对1号和2号农场的15周龄，3号农场的14周龄的VSC进行了测量，其中有1083个基因型（约50 K SNP）。使用ssGBLUP估算具有生殖性状的VSC的遗传参数。使用BayesB进行了VSC的全基因组关联研究（GWAS）。对于跨数据集的VSC表型分析，确定了性能差异，对于农场和VSC之间的相互作用，死亡总数（TND）产生了显着影响（P≤0.05），而总数发生趋势（P <0.10）出生（TNB）。在TNB，活产数（NBA），TND，死胎数（NSB）和木乃伊数（MUM）上，VSC-S与VSC-M + L有显着（P≤0.05）的预定对比。VSC作为分类性状（VSCc）和定量性状（VSCq）的遗传力估计值在整个场中分别为0.40±0.02和0.83±0.02，对于Farm1分别为0.13±0.07和0.20±0.10，对于Farm1、0.07±0.07和对于Farm2，分别为0.09±0.09，对于Farm3，分别为0.20±0.03和0.34±0.05。对于跨农场，TNB（0.28±0.19）和NBA（0.26±0.17）的遗传相关性估计良好。在农场中，发现农场1的TNB（0.61±0.47）和MUM（0.69±0.47）的VSC与生殖性状之间的中等遗传相关性，直到首次分娩之前的服务数量（NS; 0.69±0.38），并且成功获得了独特的服务农场3的第一胎（SFS；-0.71±0.38）。鉴定了与VSCc相关的多个基因组区域。其中，位于3号染色体上33-34 Mb的QTL约占VSCc和VSCq遗传变异的7.1％。该区域具有与猪早期胚胎发育有关的PRM1基因。研究结果支持VSC可能具有提高初次生产性能的繁殖效率的潜力，但结果可能取决于环境因素与VSC之间的相互作用，