鸡啄羽相残行为及其MHC味型社会识别的调控

In poultry, feather pecking (FP) is associated with cannibalism and severe welfare problems. It is a dramatic example of a spiteful behavior which reduces the victim's fitness seriously and provides no immediate direct benefit to the perpetrator. However, FP proximate mechanisms and ultimate causes, such as its evolution, social motivation, neurophysiology modulation, and complex interactions between inherited traits ("nature", aggressive behavior?) and experience ("nurture", learning behavior?), are neither understood very well nor fully characterized.We assume that high frequency FP is initiated into offensiveness, and familiarity can inhibit aggressive FP. So, we here put forward three hypotheses to approach the topic for regulating FP changes by social recognition in domestic fowls: 1) social tolerance is associated with social environment richness and determined by the level of familiarity with other individuals/its odor, 2) volatile compounds of preen gland secretions are candidate odorants which may be mediated bird's social recognition, and 3) individual genotypes of the major histocompatibility complex (MHC, a key gene complex in vertebrate immune function) are associated with their individual odortypes. In order to study effects of familiarity on social tolerance, we will compare differences in FP frequency between familiar groups and strange groups in chickens (Gallus gallus domesticus). We will also investigate effects of social environment richness and stocking density on FP. Then, we will implement odorant experiments to test the relationship between FP and social odor recognition based on familiarity. Furthermore, we plan to identify individual odortypes and MHC genotypes in the birds from the behavioral/odorant experiments respectively, so as to demonstrate association of MHC genotypes with social odor recognition. Using gas chromatography-mass spectrometry (GC-MS) to clarify volatile compound profiles of preen gland secretions, we will survey and evaluate individual odortypes in these chickens. We also try to use noninvasive genetic sampling of plumage/feces versus blood to extract DNA and compare three MHC typing methods to determine the individual MHC genotypes, including restriction fragment length polymorphism based on polymerase chain reaction (PCR-RFLP), single-strand conformation polymorphism (SSCP), and reference strand conformation analysis (RSCA). Finally, we will combine and analyze these data to provide a good evidence for the assumption that social recognition based on familiar MHC odortypes can improve social tolerance and inhibit aggressive FP in poultry.

啄羽行为，近来愈加受到动物福利研究领域的关注。啄羽会引发鸡群内同类相残，因而严重影响着鸡群健康与福利。然而，学术界至今对啄羽行为的起因、是否具攻击性属性、生理机制和遗传基础等问题尚未取得共识。本项目以熟悉性划分社群关系，基于"社会识别调节攻击性啄羽行为"的假设，展开如下研究：1）结合社群环境丰富度及密度，通过个体刺激的社会识别实验以研究熟悉性的社会容忍度效应，探讨啄羽相残的社群动机和诱因；2）以尾脂腺作候选气味源，基于气味刺激的社会识别实验探讨气味及其熟悉对鸡只社会识别的介导作用；3）测定刺激个体/刺激气味供体与实验个体的MHC基因多态性以探讨鸡只MHC基因型与其气味社会识别的关系，从而探讨MHC味型（MHC基因型决定的个体气味）的社会识别与鸡啄羽行为变化的关系。本研究主要将为控制啄羽行为提供基础性的行为遗传学参数，其次对理解动物相残行为、以及气味识别与鸟类社会行为的关系也有着积极意义

本项目研究内容包括：1）鸡啄羽行为相关的MHC基因种内和跨种多态性基础；2）鸡啄羽行为相关的PMEL17基因和嗅觉基因COR7多态性；3）啄羽行为与社会容忍度和环境丰富度的关系；4）DNA甲基化与MHC基因多态性适应。本研究调查了蛋鸡啄羽行为发生的阈值（社会容忍度）与舍饲环境丰富度关系，以及社群关系对鸡只啄羽行为的效应，以及随着饲养密度变化的社会容忍度动态。通过探讨与攻击性啄羽行为有关的MHC基因种内和种间多态性，理解到多位点等位基因分析有助于MHC基因分型。尤其是，分析MHC II DQB/DRB多位点等位基因的种内多态性，可为研究MHC基因分型和种内亲属关系可提供良好的依据。探讨嗅觉基因COR7A和PMEL17基因多态性，有助于理解多基因调控行为的假说。研究DNA甲基化有助于理解种群表观遗传多样性，那么DNA甲基化与MHC基因型多态性的关系自然也是下一步研究所关注的焦点。