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

奶牛养殖场疾病发生的记录受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)特征对控制疾病至关重要，对于遗传力高得多的动物(~0.25)，免疫反应(IR)特征被更好地定义。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，但对IR的选择应该是一种更有效的方式，可以增加对广泛病原体的抵抗力，而不是对疾病性状的直接选择。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预计会有健康优势。在圭尔夫大学，研究人员开发了一种获得专利的测试系统，以识别具有增强或高免疫反应(HIR)的动物。HIR奶牛的患病风险较低(如乳房炎、子宫炎、酮病)，对商业疫苗(如J5大肠杆菌)的反应较好，与低或中等免疫反应者相比，初乳质量有所改善。预计HIR动物需要较少的治疗干预，包括抗生素，从而改善牛奶和肉类的质量。我们的小组最近还证明，有可能识别出高、中和低免疫应答的奶牛公牛。这意味着生产者可以选择公猪来帮助改善整体牛群健康。正在进行的研究集中于了解更多关于影响这些独特和重要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，以寻找与免疫应答相关的遗传标记。这项拟议的研究结果有望为免疫反应性状在遗传选择中的潜在应用提供新的见解，以改善加拿大奶牛的内在健康并减少疾病的发生。

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.