Thekkoot D M, Young J M, Rothschild M F, Dekkers J C M
J Anim Sci. 2016 Jun;94(6):2317-31. doi: 10.2527/jas.2015-0258.
Lactation is an economically and biologically important phase in the life cycle of sows. Short generation intervals in nucleus herds and low heritability of traits associated with lactation along with challenges associated with collecting accurate lactation performance phenotypes emphasize the importance of using genomic tools to examine the underlying genetics of these traits. We report the first genomewide association study (GWAS) on traits associated with lactation and efficiency in 2 lines of Yorkshire pigs that were divergently selected for residual feed intake during grow-finish phase. A total of 862 farrowing records from 2 parities were analyzed using a Bayesian whole genome variable selection model (Bayes B) to locate 1-Mb regions that were most strongly associated with each trait. The GWAS was conducted separately for parity 1 and 2 records. Marker-based heritabilities ranged from 0.03 to 0.39 for parity 1 traits and from 0.06 to 0.40 for parity 2 traits. For all traits studied, around 90% of genetic variance came from a large number of genomic regions with small effects, whereas genomic regions with large effects were found to be different for the same trait measured in parity 1 and 2. The highest percentage of genetic variance explained by a 1-Mb window for each trait ranged from 0.4% for feed intake during lactation to 4.2% for back fat measured at farrowing in parity 1 sows and from 0.2% for lactation feed intake to 5.4% for protein mass loss during lactation in parity 2 sows. A total of thirteen 1-Mb nonoverlapping windows were found to explain more than 1.5% of genetic variance for either a single trait or across multiple traits. These 1-Mb windows were on chromosomes 2, 3, 6, 7, 8, 11, 14, 15, 17, and 18. The major positional candidate genes within 1 Mb upstream and downstream of these windows were , (SSC2), (SSC6) (SSC7), (SSC8), (SSC11), (SSC14), (SSC17). Further validation studies on larger populations are required to validate these findings and to improve our understanding of the biology and complex genetic architecture of traits associated with sow lactation performance.
泌乳期是母猪生命周期中在经济和生物学方面都很重要的阶段。核心猪群的世代间隔短，与泌乳相关性状的遗传力低，以及收集准确的泌乳性能表型所面临的挑战，都凸显了使用基因组工具来研究这些性状潜在遗传学的重要性。我们报告了对两个约克夏猪品系中与泌乳和效率相关性状的首次全基因组关联研究（GWAS），这两个品系在生长育肥阶段根据剩余采食量进行了差异选择。使用贝叶斯全基因组变量选择模型（Bayes B）对来自2个胎次的总共862条产仔记录进行分析，以定位与每个性状关联最紧密的1兆碱基（Mb）区域。GWAS分别针对第1胎和第2胎的记录进行。第1胎性状基于标记的遗传力范围为0.03至0.39，第2胎性状为0.06至0.40。对于所有研究的性状，约90%的遗传变异来自大量效应较小的基因组区域，而对于第1胎和第2胎测量的同一性状，发现效应较大的基因组区域有所不同。每个性状由1-Mb窗口解释的遗传变异最高百分比范围从第1胎母猪泌乳期采食量的0.4%到分娩时背膘厚的4.2%，以及从第2胎母猪泌乳期采食量的0.2%到泌乳期蛋白质损失量的5.4%。总共发现13个不重叠的1-Mb窗口可解释单个性状或多个性状超过1.5%的遗传变异。这些1-Mb窗口位于第2、3、6、7、8、11、14、15、17和18号染色体上。这些窗口上下游1 Mb范围内的主要位置候选基因分别是 ，（猪2号染色体），（猪6号染色体）（猪7号染色体），（猪8号染色体），（猪11号染色体），（猪14号染色体），（猪17号染色体）。需要在更大的群体上进行进一步的验证研究，以验证这些发现，并增进我们对与母猪泌乳性能相关性状的生物学和复杂遗传结构的理解。
