Ye X, Avendano S, Dekkers J C M, Lamont S J
Department of Animal Science and Center for Integrated Animal Genomics, Iowa State University, Ames 50011, USA.
Poult Sci. 2006 Sep;85(9):1555-69. doi: 10.1093/ps/85.9.1555.
Elite populations of farm animals under genetic selection are often maintained in high hygiene conditions, yet the commercial populations may be raised in, and are expected to perform well in, environments of varied hygiene levels. This presents special challenges to genetically improve those traits for which genotype by environment interactions are important. Twelve immune-related genes were studied for associations with general mortality and other performance traits in 3 elite commercial broiler chicken lines raised in high and low hygiene environments. The genes were toll-like receptor 4, MD-2 (accessory' protein of TLR4), interferon-gamma, transforming growth factor-beta3, inducible nitric oxide synthase, macrophage migration inhibitory factor, interleukin-2, caspase-1, inhibitor of apoptosis protein-1, tumor necrosis factor-related apoptosis-inducing ligand, chicken B-cell marker, and bone morphogenetic protein-7. From a total of 56 identified single-nucleotide polymorphisms (SNP) in 12 genes, 14 SNP that had moderate allelic frequencies in at least 2 of the 3 lines were typed in about 100 progeny-tested sires from each of 3 elite commercial broiler chicken lines using restriction fragment length polymorphism techniques and then used in association analysis. The traits measured on the progeny (total progeny = 145,467) were: mortality from hatching to 14 d and from 14 to 40 d of age, BW at 7 and 40 d of age, feed conversion, ultrasound breast depth, percentage of breast, eviscerated carcass weight, twisted legs or evident tibial dyschondroplasia, x-ray-inspection-based subclinical or incipient development of tibial dyschondroplasia, curly or crooked toes or bowed legs, oxygen content of blood, and female's antibody titer to infectious bursal disease virus at 27 wk. Association analyses were conducted with allele and haplotype substitution effect models using progeny mean data adjusted for fixed and mate effects as sire trait records. Ten of the 12 genes had SNP associations with at least 1 trait. Most detected effects were with mortality and growth traits. Most gene-SNP trait associations varied by genetic line or with environment. These results indicate that associations of candidate genes with important broiler traits can be identified in multiple environments, and they offer a potential for the implementation of marker-assisted selection for traits expressed in the environment in which the commercial broiler needs to perform. The effects of these immune-related candidate genes, however, are complex and affected by genetic background and environment.
经过基因选择的优质农场动物群体通常饲养在高卫生条件下，然而商业群体可能在不同卫生水平的环境中饲养，并预期在这种环境下表现良好。这给通过基因改良那些受基因型与环境互作影响较大的性状带来了特殊挑战。对在高卫生和低卫生环境中饲养的3个优质商业肉鸡品系的12个免疫相关基因与总体死亡率及其他生产性能性状的关联性进行了研究。这些基因分别是Toll样受体4、MD-2（TLR4的辅助蛋白）、γ-干扰素、转化生长因子-β3、诱导型一氧化氮合酶、巨噬细胞移动抑制因子、白细胞介素-2、半胱天冬酶-1、凋亡抑制蛋白-1、肿瘤坏死因子相关凋亡诱导配体、鸡B细胞标志物和骨形态发生蛋白-7。在12个基因中总共鉴定出56个单核苷酸多态性（SNP），其中14个在3个品系中至少2个具有中等等位基因频率的SNP，使用限制性片段长度多态性技术在3个优质商业肉鸡品系的约100只经过后代测试的父本中进行分型，然后用于关联分析。对后代测定的性状（后代总数 = 145,467）包括：从孵化到14日龄以及从14到40日龄的死亡率、7日龄和40日龄时的体重、饲料转化率、超声测定的胸深、胸肌百分比、去内脏胴体重、腿部扭曲或明显的胫骨软骨发育不良、基于X射线检查的胫骨软骨发育不良亚临床或初期发育、脚趾卷曲或弯曲或腿部弯曲、血液含氧量以及27周龄时雌性对传染性法氏囊病病毒的抗体效价。使用针对固定效应和配偶效应进行调整的后代均值数据作为父本性状记录，采用等位基因和单倍型替代效应模型进行关联分析。12个基因中的10个基因的SNP与至少1个性状存在关联。大多数检测到的效应与死亡率和生长性状有关。大多数基因-SNP性状关联因遗传品系或环境而异。这些结果表明，可以在多种环境中鉴定候选基因与重要肉鸡性状的关联，并且它们为在商业肉鸡需要表现的环境中对所表达的性状实施标记辅助选择提供了潜力。然而，这些免疫相关候选基因的效应是复杂的，并且受遗传背景和环境的影响。
