Richardson Ian W, Bradley Dan G, Higgins Isabella M, More Simon J, McClure Jennifer, Berry Donagh P
Animal and Grassland Research and Innovation Center, Teagasc, Moorepark, Fermoy, Co, Cork, Ireland.
Genet Sel Evol. 2014 Nov 18;46(1):77. doi: 10.1186/s12711-014-0077-1.
Infection of livestock with bovine tuberculosis (bTB; Mycobacterium bovis) is of major economical concern in many countries; approximately 15 000 to 20 000 cattle are infected per year in Ireland. The objective of this study was to quantify the genetic variation for bTB susceptibility in Irish dairy and beef cattle.
A total of 105 914 cow, 56 904 heifer and 21 872 steer single intra-dermal comparative tuberculin test records (i.e., binary trait) collected from the years 2001 to 2010 from dairy and beef herds were included in the analysis. Only animal level data pertaining to periods of herd bTB infection were retained. Variance components for bTB were estimated using animal linear and threshold mixed models and co-variances were estimated using sire linear mixed models.
Using a linear model, the heritability for susceptibility to bTB in the entire dataset was 0.11 and ranged from 0.08 (heifers in dairy herds) to 0.19 (heifers in beef herds) among the sub-populations investigated. Differences in susceptibility to bTB between breeds were clearly evident. Estimates of genetic correlations for bTB susceptibility between animal types (i.e., cows, heifers, steers) were all positive (0.10 to 0.64), yet different from one. Furthermore, genetic correlations for bTB susceptibility between environments that differed in herd prevalence of bTB ranged from 0.06 to 0.86 and were all different from one.
Genetic trends for bTB susceptibility observed in this study suggest a slight increase in genetic susceptibility to bTB in recent years. Since bTB is of economic importance and because all animals are routinely tested at least once annually in Ireland and some other countries, the presence of genetic variation for bTB susceptibility suggests that bTB susceptibility should be included in a national breeding program to halt possible deterioration in genetic susceptibility to bTB infection.
牛结核病（bTB；牛分枝杆菌）感染家畜在许多国家是一个主要的经济问题；在爱尔兰，每年约有15000至20000头牛感染。本研究的目的是量化爱尔兰奶牛和肉牛对bTB易感性的遗传变异。
分析中纳入了2001年至2010年从奶牛和肉牛群收集的总共105914头母牛、56904头小母牛和21872头公牛的单次皮内比较结核菌素试验记录（即二元性状）。仅保留与牛群bTB感染期相关的个体水平数据。使用动物线性和阈值混合模型估计bTB的方差成分，使用父系线性混合模型估计协方差。
使用线性模型，整个数据集中对bTB易感性的遗传力为0.11，在所研究的亚群体中，范围从0.08（奶牛群中的小母牛）到0.19（肉牛群中的小母牛）。不同品种对bTB易感性的差异明显。动物类型（即母牛、小母牛、公牛）之间bTB易感性的遗传相关性估计均为正（0.10至0.64），但均不等于1。在bTB牛群患病率不同的环境之间，bTB易感性的遗传相关性范围为从0.06到0.86，且均不等于1。
本研究中观察到的bTB易感性遗传趋势表明，近年来对bTB的遗传易感性略有增加。由于bTB具有经济重要性，并且在爱尔兰和其他一些国家所有动物每年至少进行一次常规检测，bTB易感性存在遗传变异表明，bTB易感性应纳入国家育种计划，以阻止对bTB感染的遗传易感性可能出现的恶化。
