Gonda M G, Chang Y M, Shook G E, Collins M T, Kirkpatrick B W
Dairy Science Department, University of Wisconsin, Madison 53706, USA.
J Dairy Sci. 2006 May;89(5):1804-12. doi: 10.3168/jds.S0022-0302(06)72249-4.
The objective of this study was to estimate genetic variability of Mycobacterium avium ssp. paratuberculosis infection in US Holsteins. Blood and fecal samples were collected primarily from daughters of 12 bulls in their second or third lactation. Routine disease testing of the sires documented that they were not infected. Herds without a "suspect" or positive ELISA (sample/positive ratio > or = 0.10) or positive fecal culture test were deleted from the data set. The remaining 4,603 cows from 238 herds and 46 sires were used to estimate heritability of M. paratuberculosis infection. Heritability was estimated with 3 Johne's disease diagnostic tests: 1) fecal culture alone, 2) serum antibody ELISA alone, and 3) both tests (combined) with a positive animal defined as all animals with either a positive fecal culture or ELISA test. Four statistical models were used to estimate heritability: 1) linear (ELISA), 2) threshold (fecal culture and combined), 3) ordered threshold (ELISA), and 4) bivariate linear-threshold (ELISA-fecal culture). A sire model and Bayesian approach using Markov chain Monte Carlo methods were used in each case. Heritability of infection based on the fecal culture test was 0.153 [posterior standard deviation (PSD) = 0.115]. Heritability with the ELISA was 0.159 (PSD = 0.090) with a linear model and 0.091 (PSD = 0.053) with an ordered threshold model. Heritability of the combined tests was 0.102 (PSD = 0.066). Heritability estimates of fecal culture and ELISA with the bivariate model varied slightly from estimates obtained with the univariate models (0.125 and 0.183, respectively), with a corresponding increase in precision (PSD = 0.096 and 0.082, respectively). This study demonstrates that exploitable genetic variation exists in dairy cattle for M. paratuberculosis infection susceptibility.
本研究的目的是评估美国荷斯坦奶牛副结核分枝杆菌感染的遗传变异性。血液和粪便样本主要采集自12头处于第二或第三泌乳期公牛的女儿。对这些公牛进行的常规疾病检测表明它们未被感染。数据集中删除了没有“可疑”或阳性ELISA（样本/阳性比率≥0.10）或粪便培养检测呈阳性的牛群。来自238个牛群的4603头母牛和46头公牛用于估计副结核分枝杆菌感染的遗传力。使用3种约翰氏病诊断测试来估计遗传力：1）仅粪便培养，2）仅血清抗体ELISA，3）两种测试（联合），将阳性动物定义为粪便培养或ELISA测试呈阳性的所有动物。使用4种统计模型来估计遗传力：1）线性（ELISA），2）阈值（粪便培养和联合），3）有序阈值（ELISA），4）双变量线性-阈值（ELISA-粪便培养）。每种情况均使用父系模型和基于马尔可夫链蒙特卡罗方法的贝叶斯方法。基于粪便培养测试的感染遗传力为0.153 [后验标准差（PSD）= 0.115]。ELISA的遗传力在线性模型中为0.159（PSD = 0.090），在有序阈值模型中为0.091（PSD = 0.053）。联合测试的遗传力为0.102（PSD = 0.066）。双变量模型中粪便培养和ELISA的遗传力估计值与单变量模型获得的估计值略有不同（分别为0.125和0.183），相应的精度有所提高（PSD分别为0.096和0.082）。本研究表明，奶牛在副结核分枝杆菌感染易感性方面存在可利用的遗传变异。
