Johne's disease in cattle is the result of infection of the small intestine by Mycobacterium avium ssp. paratuberculosis (MAP), leading to an incurable inflammatory bowel disease (Johne's disease or paratuberculosis). The disease is a concern both for its direct cost to dairy producers and for its zoonotic potential. The objective of this study was to estimate the heritability for susceptibility to infection of cattle by MAP using Johne's testing records (ELISA test for presence of antibodies to MAP in milk or blood) from US Holstein cattle from 2009 to 2016. Data sets were edited to include records from herds with 100 or more total records and sires with 50 or more daughters. Data sets were further edited to include (1) only herds with at least 1 positive test, (2) herds with at least 2.5% positive test results, and (3) herds with at least 5% positive test results to examine the effect of data from herds with higher proportions of positive tests, and presumably higher pathogen exposure, on heritability estimates. Two models were used in this study, a linear sire model and a binary threshold-probit sire model. Both were mixed models considering fixed effects of herd and age at test, the latter as a covariate accounting for linear and quadratic effects; random effects included sire and residual. Analyses were conducted using a restricted maximum likelihood method. Heritability estimates (±standard error) from the linear model were 0.041 ± 0.004, 0.050 ± 0.004, and 0.062 ± 0.007 for data from herds with at least 1 positive test, ≥2.5% positive tests, and ≥5% positive tests, respectively. Heritability estimates from the threshold model were 0.157 ± 0.014, 0.174 ± 0.016, and 0.186 ± 0.021 for data from herds with at least 1 positive test, ≥2.5% positive tests, and ≥5% positive tests, respectively. Heritability estimates from the linear model were affected by population incidence for positive tests, in contrast to estimates from the threshold model, likely accounting for the difference in magnitude of heritability estimates between models and suggesting that the threshold model analysis is the better choice. Heritability estimates increased as data were restricted to herds with presumed higher MAP exposure for both linear model and threshold model analyses. These estimates are similar to previous estimates in other dairy cattle populations and suggest the potential for selection to lessen susceptibility to MAP infection.

牛的约翰尼氏病是鸟分枝杆菌属ssp感染小肠的结果。副结核病（MAP），导致无法治愈的炎症性肠病（约翰氏病或肺结核）。该疾病不仅给乳制品生产商带来直接成本，而且还具有人畜共患病的潜力。这项研究的目的是使用Johne的2009年至2016年美国霍尔斯坦牛的检测记录（牛奶或血液中MAP抗体的存在的ELISA检测）来估计MAP对牛感染的易感性。包括来自牧群的记录（总数超过100个）和父亲（育有50个或更多女儿）。进一步编辑数据集以包括（1）仅具有至少1个阳性测试的牛群，（2）具有至少2.5％阳性测试结果的牛群，以及（3）具有至少5％阳性测试结果的牛群，以检查来自阳性检测比例较高的牛群的数据，以及根据遗传力估计的病原体暴露。在这项研究中使用了两个模型，一个线性公母模型和一个二进制阈值-概率公母模型。两者都是混合模型，考虑了牛群和受试年龄的固定影响，后者是线性和二次影响的协变量。随机影响包括父亲和父亲。使用限制最大似然法进行分析。线性模型的遗传力估计值（±标准误差）分别是至少有1个阳性试验，≥2.5％阳性试验和≥5％阳性试验的牛群数据的0.041±0.004、0.050±0.004和0.062±0.007。对于至少进行1次阳性测试，≥2.5％阳性测试和≥5％阳性测试的人群数据，阈值模型的遗传力估计值为0.157±0.014、0.174±0.016和0.186±0.021，分别。与阈值模型的估计相比，线性模型的遗传力估计值受阳性试验人群发生率的影响，这可能解释了模型之间的遗传力估计值的大小差异，这表明阈值模型分析是更好的选择。对于线性模型和阈值模型分析，由于数据仅限于具有较高MAP暴露的牛群，因此遗传力估计值增加。这些估计值与其他奶牛种群中的先前估计值相似，并表明了进行选择以减轻对MAP感染的敏感性的潜力。可能考虑了模型之间的遗传力估计值的大小差异，并表明阈值模型分析是更好的选择。对于线性模型和阈值模型分析，由于数据仅限于具有较高MAP暴露的牛群，因此遗传力估计值增加。这些估计值与其他奶牛种群中的先前估计值相似，并表明了进行选择以减轻对MAP感染的敏感性的潜力。可能考虑了模型之间的遗传力估计值的大小差异，并表明阈值模型分析是更好的选择。对于线性模型和阈值模型分析，由于数据仅限于具有较高MAP暴露的牛群，因此遗传力估计值增加。这些估计值与其他奶牛种群中的先前估计值相似，并表明了进行选择以减轻对MAP感染的敏感性的潜力。