CSIRO Agriculture & Food, Queensland Bioscience Precinct, St. Lucia, Brisbane, QLD, Australia.
CSIRO Agriculture & Food, F.D. McMaster Laboratory, Chiswick, New England Highway, Armidale, NSW, Australia.
J Anim Sci. 2021 Mar 1;99(3). doi: 10.1093/jas/skaa384.
In animal breeding and genetics, the ability to cope with disease, here defined as immune competence (IC), with minimal detriment to growth and fertility is a desired objective which addresses both animal production and welfare considerations. However, defining and objectively measuring IC phenotypes using testing methods which are practical to apply on-farm has been challenging. Based on previously described protocols, we measured both cell-mediated immune response (Cell-IR) and antibody-mediated immune response (Ab-IR) and combined these measures to determine an animal's IC. Using a population of 2,853 Australian Angus steers and heifers, we compared 2 alternative methods to combine both metrics into a single phenotype to be used as a tool for the genetic improvement of IC. The first method, named ZMEAN, is obtained by taking the average of the individual metrics after subjecting each to a Z-score standardization. The second, ImmuneDEX (IDEX), is a weighted average that considers the correlation between Cell-IR and Ab-IR, as well as the difference in ranking of individuals by each metric, and uses these as weights in the averaging. Both simulation and real data were used to understand the behavior of ZMEAN and IDEX. To further ascertain the relationship between IDEX and other traits of economic importance, we evaluated a range of traits related to growth, feedlot performance, and carcass characteristics. We report estimates of heritability of 0.31 ± 0.06 for Cell-IR, 0.42 ± 0.06 for Ab-IR, 0.42 ± 0.06 for ZMEAN and 0.370 ± 0.06 for IDEX, as well as a unity genetic correlation (rg) between ZMEAN and IDEX. While a moderately positive rg was estimated between Cell-IR and Ab-IR (rg = 0.33 ± 0.12), strongly positive estimates were obtained between IDEX and Cell-IR (rg = 0.80 ± 0.05) and between IDEX and Ab-IR (rg = 0.85 ± 0.04). We obtained a moderately negative rg between IC traits and growth including an rg = -0.38 ± 0.14 between IDEX and weaning weight, and negligible with carcass fat measurements, including an rg = -0.03 ± 0.12 between IDEX and marbling. Given that breeding with a sole focus on production might inadvertently increase susceptibility to disease and associated antibiotic use, our analyses suggest that ImmuneDEX will provide a basis to breed animals that are both highly productive and with an enhanced ability to resist disease.
在动物育种和遗传学中，具备最小程度损害生长和繁殖力即可应对疾病的能力，即免疫能力（IC），这是一个理想的目标，既涉及动物生产又涉及福利考量。然而，使用实际可行的农场测试方法来定义和客观测量 IC 表型一直具有挑战性。根据先前描述的方案，我们测量了细胞介导的免疫反应（Cell-IR）和抗体介导的免疫反应（Ab-IR），并将这些测量结果结合起来以确定动物的 IC。使用 2853 头澳大利亚安格斯公牛和小母牛的群体，我们比较了 2 种替代方法，将这两个指标组合成一个单一的表型，用作提高 IC 遗传能力的工具。第一种方法称为 ZMEAN，通过对每个指标进行 Z 分数标准化后取平均值获得。第二种方法称为 ImmuneDEX（IDEX），是一种加权平均值，它考虑了 Cell-IR 和 Ab-IR 之间的相关性，以及每个指标对个体排名的差异，并将这些作为平均值的权重。我们使用模拟和真实数据来了解 ZMEAN 和 IDEX 的行为。为了进一步确定 IDEX 与其他具有经济重要性的性状之间的关系，我们评估了与生长、育肥性能和胴体特征相关的一系列性状。我们报告的 Cell-IR 的遗传力估计值为 0.31 ± 0.06，Ab-IR 的遗传力估计值为 0.42 ± 0.06，ZMEAN 的遗传力估计值为 0.42 ± 0.06，IDEX 的遗传力估计值为 0.370 ± 0.06，以及 ZMEAN 和 IDEX 之间的单位遗传相关系数（rg）为 0.37。虽然 Cell-IR 和 Ab-IR 之间估计的 rg 为中度正相关（rg = 0.33 ± 0.12），但 IDEX 和 Cell-IR 之间的 rg 估计值较高（rg = 0.80 ± 0.05），IDEX 和 Ab-IR 之间的 rg 估计值较高（rg = 0.85 ± 0.04）。我们在 IC 性状和生长之间获得了中度负相关，包括 IDEX 和断奶体重之间的 rg = -0.38 ± 0.14，以及胴体脂肪测量值之间的相关性很小，包括 IDEX 和大理石花纹之间的 rg = -0.03 ± 0.12。鉴于仅仅专注于生产的繁殖可能会无意中增加对疾病的易感性并增加抗生素的使用，我们的分析表明，ImmuneDEX 将为培育既高产又具有增强抵抗疾病能力的动物提供基础。
