Effects of the use of cloning technique on breeding structure of domestic animal populations

采用统计遗传学方法，在肉牛育种的三种典型情况下，对克隆技术的应用效率进行了评价.使用克隆作为商业储备的直观优点是增加了最终产品的一致性。根据相关系数和克隆间差异的标准误差来评估该期望值。结果表明，克隆体比其他的亲缘关系对在某种程度上更加一致，但并不像大多数人所期望的那样一致。克隆测定作为常规后代测定的替代方法，从选择的准确性方面评价了克隆测定的效率。研究发现，在某些情况下，根据显性变异的大小和试验动物的数量，常规的子代测定优于克隆测定.克隆公公牛的使用（1）找到“超级”公公牛的概率“超级”公公牛的定义是一头公牛，它的表现突出，足以证明它的克隆是合理的。使用确定性模型，我们可以找到一个“超级”父系的概率进行了计算。结果表明，在一个中等遗传增益的群体中，这种概率是很低的。(2)克隆种公牛的使用对遗传多样性的影响应用随机模拟技术对日本黑牛的系谱记录，研究了克隆种公牛的使用对遗传多样性的影响。在一个曾被大量使用过供体父系的种群中，使用他的克隆体将导致遗传多样性的急剧减少。

The efficiencies of the use of cloning technique were evaluated under three typical situations of beef cattle breeding, by means of statistical genetics methods.1. Use of clones as commercial stockThe intuitive merit of the use of clones as commercial stock is the increase in uniformity of final products. This expectation was evaluated in terms of the coefficient of correlation and the standard error of difference between clones. It was shown that clones would be somewhat more uniform than other pairs of relatives, but would not be as uniform as most people would expect.2. Clone testingThe efficiency of clone testing as an alternative to the conventional progeny testing was evaluated in terms of the accuracy of selection. It was found that there are situations under which the conventional progeny testing is preferable to the clone testing, depending on the amount of dominance variation and the number of tested animals.3. Use of cloned sires(1) Probability of finding a "super" sireA "super" sire is defined as a bull who has a prominent performance enough to justify to make his clones. Using a deterministic model, the probability that we can find a "super" sire was calculated. The results showed that in a population with a moderate genetic gain, the probability would be quite low.(2) Effect of the use of cloned sires on genetic diversityApplying a stochastic simulation technique to pedigree records of Japanese Black cattle, the effect of the use of cloned sires on genetic diversity was examined. In a population in which the donor sire had been intensively used, the use of his clones would lead to a drastic reduction of genetic diversity.