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

牛场疾病发生的记录受到许多环境因素的影响，包括数据记录做法、牛群管理和病原体暴露。因此，疾病性状的遗传力很低，一般在0.10以下。另一方面，免疫反应（IR）性状对控制疾病至关重要，并且具有更高的遗传率（~0.25），可以更好地定义每种动物。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选择应该是增强对广泛病原体抗性的更有效方法。事实上，免疫系统是用来控制疾病的，能够做出强大免疫反应的人对健康有好处。圭尔夫大学的研究人员开发了一种专利测试系统，用于识别具有增强或高免疫反应（HIR）的动物。与低免疫应答者或平均免疫应答者相比，HIR奶牛患病风险（如乳腺炎、子宫炎、酮症）较低，对商业疫苗（如J5大肠杆菌）反应更好，初乳质量也有所改善。预计HIR动物需要较少的治疗干预，包括抗生素，从而改善奶和肉的品质。我们的小组最近也证明，有可能识别高，平均和低免疫反应的乳制品品种。这意味着生产者可以选择HIR品种来帮助改善牛群的整体健康状况。正在进行的研究重点是了解更多影响这些独特和重要表型的遗传和表观遗传机制。下一步提高对HIR技术的理解的关键步骤之一是进行全基因组关联研究，以寻找与免疫反应性相关的遗传标记。拟议的研究结果有望为在遗传选择中潜在地包括免疫反应特征提供新的见解，以改善加拿大奶牛的内在健康和减少疾病的发生。

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.