1INRA, UR83, 37380 Nouzilly, France.
Animal. 2008 Oct;2(10):1518-25. doi: 10.1017/S1751731108002784.
Mule duck, a cross between a Muscovy drake and a Pekin female, is reported by the farmers to frequently express fear behaviours, such as man avoidance. The genetic basis of fear responses in mule ducks was therefore investigated in this study. According to a previous experiment, the dominant effect of Pekin genotype was hypothesised; however, due to the absence of birds from the reciprocal cross, a superiority of the Pekin in additive effect could not be distinguished from a direct maternal additive effect. In order to clarify this, ducks from the mule genotype, the two parental genotypes (Pekin and Muscovy) and the reciprocal intercross (hinny) underwent a set of physiological and individual behavioural tests of fear. Both parental genotypes were highly fearful but exhibited responses of different patterns: Pekin ducks manifested a higher locomotor activity, whereas the Muscovy ducks showed a higher avoidance to man. Hybrids expressed higher panic responses and specific fear of man than the two parent breeds. Both hybrids expressed similar patterns and the maternal effects were not significant. Significant heterosis effects were found for most of the behavioural responses, in agreement with the fact that higher fear responses were expressed by the hybrids compared to the parental genotypes. A significant heterosis effect was also found for basal adrenal activity; hybrids having higher basal level than parental genotypes. Maximum capacity of adrenal response appeared to be determined by direct additive effects with a superiority of the Pekin genotype.
骡鸭是由麝香鸭公鸭和北京鸭母鸭杂交而成的，据农民报告，骡鸭经常表现出恐惧行为，例如躲避人类。因此，本研究调查了骡鸭恐惧反应的遗传基础。根据之前的一项实验，假设北京鸭基因型具有显性效应；然而，由于缺乏来自相互杂交的鸟类，北京鸭在加性效应上的优势无法与直接母性加性效应区分开来。为了澄清这一点，来自骡鸭基因型、两个亲本品系（北京鸭和麝香鸭）和互交杂种（骡鸭）的鸭子进行了一系列恐惧的生理和个体行为测试。两个亲本品系都非常害怕，但表现出不同的反应模式：北京鸭表现出更高的运动活性，而麝香鸭表现出更高的对人类的回避。杂种鸭比两个亲本品系表现出更高的恐慌反应和对人类的特定恐惧。这两种杂种鸭表现出相似的模式，母性效应不显著。大多数行为反应都发现了显著的杂种优势效应，这与杂种鸭比亲本品系表现出更高的恐惧反应的事实一致。基础肾上腺活动也发现了显著的杂种优势效应；杂种鸭的基础水平高于亲本品系。肾上腺反应的最大能力似乎取决于直接加性效应，北京鸭基因型具有优势。
