ARS-USDA, U.S. Meat Animal Research Center, Clay Center, NE 68933, USA.
J Anim Sci. 2013 Aug;91(8):3564-73. doi: 10.2527/jas.2012-5911. Epub 2013 Jun 4.
Bovine respiratory disease (BRD) is the most economically important disease in U.S. feedlots. Infection can result in morbidity, mortality, and reduced average daily gain. Cheap and reliable genetic methods of prediction and protection from BRD would be highly advantageous to the industry. The immune response may correlate with BRD incidence. Cattle (n = 2,182) were vaccinated against common viral and bacterial pathogens of BRD. Two blood samples were collected, one during booster vaccination and one 21d later, enabling 3 phenotypes for each trait [prebooster (pre), postbooster (post), and delta (post minus pre)]. From the blood samples innate and adaptive responses [counts of white blood cells (WBC), neutrophils, lymphocytes, monocytes, eosinophils, and basophils] were measured. In addition, feedlot ADG and binary traits [health records (HR; 0 = healthy, 1 = ill) and lung scores (LS; collected at harvest; 0 = no lesions, 1 = lesions)] were also recorded. Traits ADG, HR, and LS have all been significantly correlated with infection to BRD. In this investigation we aimed to find correlations between the immune response and ADG, HR, and LS to find an easily measurable trait that would be a good predictor of BRD resistance after vaccination. The results showed an average positive delta for the innate immune response (eosinophils, basophils, neutrophils), whereas the adaptive immune response had an average negative delta (lymphocytes). Overall, we discovered that the immune responses had moderately high heritabilities (h(2); lowest: delta monocytes, 0.21 ± 0.05; greatest: pre lymphocytes: 0.5 ± 0.05), with lymphocytes having the greatest h(2) throughout the study (h(2) ≥ 0.41). All genetic correlations were calculated using bivariate REML models. Although LS did not significantly correlate with any of the immune phenotypes, both ADG (post lymphocytes, -0.24 ± 0.12) and HR (pre eosinophils, -0.67 ± 0.29; delta WBC, -0.5 ± 0.24, and delta lymphocytes, -0.67 ± 0.21) did. All the significant genetic correlations with HR were negative; resistance to BRD appears to be a function of greater delta lymphocytes and WBC. The increase in eosinophils may potentially link its role in decreasing lymphocytes. These results may enable producers to predict if revaccination, quarantine, and breeding of animals is required to reduce the incidence of BRD postvaccination. In addition, immunological phenotypes maybe used to aid genomic selection indices to select animals with greater rates of protection after BRD vaccination.
牛呼吸道疾病（BRD）是美国饲养场最重要的经济疾病。感染会导致发病率、死亡率和平均日增重降低。廉价且可靠的预测和预防 BRD 的遗传方法将对该行业非常有利。免疫反应可能与 BRD 发病率相关。对 2182 头牛进行了针对 BRD 常见病毒和细菌病原体的疫苗接种。采集了两份血样，一份在加强免疫时采集，另一份在 21 天后采集，每个性状都有 3 种表型[加强免疫前（pre）、加强免疫后（post）和变化值（post 减去 pre）]。从血液样本中测量了先天和适应性反应[白细胞（WBC）计数、中性粒细胞、淋巴细胞、单核细胞、嗜酸性粒细胞和嗜碱性粒细胞]。此外，饲养场的平均日增重（ADG）和二元性状[健康记录（HR；0=健康，1=患病）和肺评分（LS；在收获时采集；0=无病变，1=病变）]也被记录下来。ADG、HR 和 LS 性状均与 BRD 感染显著相关。在这项研究中，我们旨在找到免疫反应与 ADG、HR 和 LS 之间的相关性，以找到一种易于测量的性状，作为疫苗接种后 BRD 抗性的良好预测指标。结果显示，先天免疫反应（嗜酸性粒细胞、嗜碱性粒细胞、中性粒细胞）的平均变化值为正，而适应性免疫反应的平均变化值为负（淋巴细胞）。总的来说，我们发现免疫反应具有较高的遗传力（h2；最低：变化值单核细胞，0.21±0.05；最高：前淋巴细胞：0.5±0.05），整个研究中淋巴细胞的 h2 最大（h2≥0.41）。所有遗传相关性均使用双变量 REML 模型计算。尽管 LS 与任何免疫表型均无显著相关性，但 ADG（后淋巴细胞，-0.24±0.12）和 HR（前嗜酸性粒细胞，-0.67±0.29；变化值 WBC，-0.5±0.24，变化值淋巴细胞，-0.67±0.21）均有相关性。所有与 HR 相关的遗传相关性均为负；对 BRD 的抵抗力似乎是 delta 淋巴细胞和 WBC 增加的功能。嗜酸性粒细胞的增加可能与其减少淋巴细胞的作用有关。这些结果可能使生产者能够预测是否需要重新接种疫苗、隔离和动物繁殖，以减少接种疫苗后 BRD 的发病率。此外，免疫表型可能用于辅助基因组选择指数，以选择接种 BRD 疫苗后保护率更高的动物。
