Genetic markers associated with high and low immune response phenotypes and its implication for disease

奶牛场疾病发生的记录受到许多环境因素的影响，包括数据记录、牛群管理和病原体暴露。结果表明，病害性状的遗传力很低，一般在0.10以下。另一方面，免疫应答（IR）性状对于控制疾病至关重要，并且对于每只动物更好地定义，具有更高的遗传力（~0.25）。因此，虽然疾病记录是验证任何改善健康的选择策略的先决条件，但与直接选择疾病性状相比，IR选择应该是一种更强大的方式来增加对广泛病原体的抗性。事实上，免疫系统的目的是控制疾病，能够产生强大免疫反应的个体预计将具有健康优势。在圭尔夫大学，研究人员开发了一种专利测试系统，以识别具有增强或高免疫反应（HIR）的动物。HIR奶牛已被证明具有较低的疾病风险（例如乳腺炎、子宫炎、酮病），对商业疫苗（例如J5 E.大肠杆菌），并且与低或平均免疫应答者相比具有改善的初乳质量。HIR动物预计需要较少的治疗干预，包括抗生素，从而改善牛奶和肉类质量。我们小组最近还证明，有可能识别出高、中、低免疫应答奶牛公畜。这意味着生产者可以选择HIR种公牛来帮助改善整体牛群健康。正在进行的研究集中在更多地了解影响这些独特而重要的表型的遗传和表观遗传机制。提高对HIR技术的理解的下一个关键步骤之一是进行全基因组关联研究，以寻找与免疫反应相关的遗传标记。拟议的研究结果预计将提供新的见解，在遗传选择的免疫反应性状的潜在列入，以改善固有的健康和减少疾病的发生在加拿大奶牛的目标。

Recording of on-farm disease occurence of dairy cattle is subject to many environmental factors, including data recording practises, herd management and pathogen exposure. As a result the heritability of disease traits are quite low, generally below 0.10. Immune response (IR) traits, on the other hand, are critical to control disease and are better defined for each animal with a much higher heritability (~0.25). Therefore, while disease recording is a prerequisite for the validation of any selection strategy to improve health, selection for IR should be a more powerful way to increase resistance to a broad range of pathogens versus direct selection on disease traits. In fact, the immune system is designed to control disease and individuals that can make a robust immune response are expected to have health advantages. At the University of Guelph, researchers have developed a patented test system to identify animals with enhanced or High Immune Response (HIR). HIR dairy cattle have been shown to be at lower risk of disease (e.g. mastitis, metritis, ketosis), respond better to commercial vaccines (e.g. J5 E. coli) and have improved colostrum quality compared to low or average immune responders. HIR animals are expected to require less therapeutic intervention, including antibiotics, thereby improving milk and meat quality. Our group has recently also demonstrated that it is possible to identify high, average and low immune responder dairy sires. This means that producers could select HIR sires to help improve overall herd health. Ongoing research is focused on learning more about the genetic and epigenetic mechanisms that influence these unique and important phenotypes. One of the next critical steps to improve understanding of the HIR technology is to perform genome-wide association studies to search for genetic markers associated with immune responsiveness. The results of the proposed study are expected to provide novel insight into the potential inclusion of immune response traits in genetic selection with the goal of improving inherent health and decrease the occurrence of disease in Canadian dairy cattle.