BACKGROUND Breeding genetically hornless, i.e. polled, cattle provides an animal welfare-friendly and non-invasive alternative to the dehorning of calves. However, the molecular regulation of the development of horns in cattle is still poorly understood. Studying genetic characters such as polledness and scurs, can provide valuable insights into this process. Scurs are hornlike formations that occur occasionally in a wide variety of sizes and forms as an unexpected phenotype when breeding polled cattle. METHODS We present a unique dataset of 885 Holstein-Friesian cattle with polled parentage. The horn phenotype was carefully examined, and the phenotypic heterogeneity of the trait is described. Using a direct gene test for polledness, the polled genotype of the animals was determined. Subsequently, the existence of a putative scurs locus was investigated using high-density genotype data of a selected subset of 232 animals and two mapping approaches: mixed linear model-based association analyses and combined linkage disequilibrium and linkage analysis. RESULTS The results of an exploratory data analysis indicated that the expression of scurs depends on age at phenotyping, sex and polled genotype. Scurs were more prevalent in males than in females. Moreover, homozygous polled animals did not express any pronounced scurs and we found that the Friesian polled allele suppresses the development of scurs more efficiently than the Celtic polled allele. Combined linkage and linkage disequilibrium mapping revealed four genome-wide significant loci that affect the development of scurs, one on BTA5 and three on BTA12. Moreover, suggestive associations were detected on BTA16, 18 and 23. The mixed linear model-based association analysis supports the results of the combined linkage and linkage disequilibrium analysis. None of the mapping approaches provided convincing evidence for a monogenic inheritance of scurs. CONCLUSIONS Our results contradict the initial and still broadly accepted model for the inheritance of horns and scurs. We hypothesise an oligogenetic model to explain the development of scurs and polledness.

中文翻译：

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杂合轮询的（Pp）牛的杂草是否具有复杂的定量特征？

背景技术遗传上无角的，即被轮询的牛的育种提供了对牛犊的去角质的对动物福利友好且非侵入性的替代方案。然而，对牛角发育的分子调控仍知之甚少。研究遗传特征，例如花粉和黑潮，可以为这一过程提供有价值的见解。cur是牛角状的，偶尔会以各种各样的大小出现，并在繁殖被轮询的牛时以意外的表型形式出现。方法我们提供了一个带有投票亲子关系的885荷斯坦-弗里斯兰牛的独特数据集。仔细检查了喇叭的表型，并描述了该性状的表型异质性。使用直接基因测试进行轮询，确定了动物的轮询基因型。后来，使用232只动物的选定子集的高密度基因型数据和两种映射方法：基于线性模型的混合关联分析以及连锁不平衡和连锁分析相结合的方法，研究了假定的杂草基因座的存在。结果一项探索性数据分析的结果表明，scurs的表达取决于表型，性别和轮询基因型的年龄。男性比女性更容易患上黑潮。此外，纯合子民意调查的动物没有表达任何明显的菌丝，我们发现弗里斯兰民意调查的等位基因比凯尔特人的民意调查的等位基因更有效地抑制了菌丝的发育。结合的连锁和连锁不平衡作图揭示了影响全基因发育的四个全基因组重要位点，一个在BTA5上，三个在BTA12上。此外，在BTA16、18和23上检测到提示性关联。基于混合线性模型的关联分析支持组合连锁和连锁不平衡分析的结果。没有一种作图方法提供了令人信服的证据来证明杂草的单基因遗传。结论我们的研究结果与最初仍被广泛接受的牛角和黑穗病遗传模型相矛盾。我们假设一个寡聚模型来解释和轮询的发展。结论我们的研究结果与最初仍被广泛接受的牛角和黑穗病遗传模型相矛盾。我们假设一个寡聚模型来解释explain虫和花粉症的发展。结论我们的研究结果与最初仍被广泛接受的牛角和黑穗病遗传模型相矛盾。我们假设一个寡聚模型来解释和轮询的发展。