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

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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.