Feather pecking (FP) is a serious economic and welfare problem in the domestic fowl. It has recently been shown that the distribution of FP bouts within groups is heterogeneous and contains a sub-population of extreme feather peckers (EFP). The present study proposed a novel model to detect EFP hens. A mixture of two negative binomial distributions was fitted to FP data of a F2 cross of about 960 hens, and, based on the results, a calculation of the posterior probability for each hen belonging to the EFP subgroup (pEFP) was done. The fit of the mixture distribution revealed that the EFP subgroup made up a proportion of one third of the F2 cross. The EFP birds came more frequently into pecking mood and showed higher pecking intensities compared to the remaining birds. Tonic immobility and emerge box tests were conducted at juvenile and adult age of the hens to relate fearfulness to EFP. After dichotomization, all traits were analyzed in a multivariate threshold model and a genomewide association study was performed. The new trait pEFP has a medium heritability of 0.35 and is positively correlated with the fear traits. Breeding for this new trait could be an interesting option to reduce the proportion of extreme feather peckers. An index of fear related traits might serve as a proxy to breed indirectly for pEFP. GWAS revealed that all traits are typical quantitative traits with many genes and small effects contributing to the genetic variance.

中文翻译：

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一种解释产蛋鸡极端羽毛啄食行为的新模型。

啄羽毛（FP）是家禽中严重的经济和福利问题。最近显示，FP反弹在组内的分布是异质的，并且包含极羽啄木鸟（EFP）的子种群。本研究提出了一种检测EFP母鸡的新颖模型。将两个负二项式分布的混合拟合到大约960只母鸡的F2杂交的FP数据，并根据结果对属于EFP子组（pEFP）的每只母鸡进行后验概率计算。混合物分布的拟合显示，EFP亚组占F2杂交的三分之一。与其余鸟类相比，EFP鸟类更经常出现啄食的情况，并且啄食强度更高。在母鸡的幼年和成年年龄进行补品固定和出箱测试，以将恐惧与EFP相关联。二分法后，在多变量阈值模型中分析所有性状，并进行全基因组关联研究。新性状pEFP具有0.35的中等遗传力，并且与恐惧性状正相关。繁殖这种新特性可能是减少极端羽毛啄木鸟比例的一种有趣的选择。与恐惧相关的性状的指数可以作为间接替代pEFP的指标。GWAS揭示，所有性状都是典型的数量性状，具有许多基因，并且影响遗传变异的影响很小。新性状pEFP具有0.35的中等遗传力，并且与恐惧性状正相关。繁殖这种新特性可能是减少极端羽毛啄木鸟比例的一种有趣的选择。与恐惧相关的性状的指数可以作为间接替代pEFP的指标。GWAS揭示，所有性状都是典型的数量性状，具有许多基因，且影响遗传变异的影响很小。新性状pEFP具有0.35的中等遗传力，并且与恐惧性状正相关。繁殖这种新特性可能是减少极端羽毛啄木鸟比例的一种有趣的选择。与恐惧相关的性状的指数可以作为间接替代pEFP的指标。GWAS揭示，所有性状都是典型的数量性状，具有许多基因，且影响遗传变异的影响很小。