Abstract
This article presents the results of Mr. Na's thesis (1972). A method to estimate genetic progress which Everett et al. (1967) applied to a simulated population of cows is tried on two real populations of cows. Data collected in 1963–1967 for the daughters and in 1948–1959 for the dams are used. The computed estimates are of little value because of the bias caused by the selection of sires. The reason why selection of bulls affects the estimation of genetic gain, which is not obvious, is described. The method seems to be appropriate for large quantities of data where adjustment for the influence of selection among sires is possible. In order to correct for age of dams, dams' performance, and selection of sires it is necessary to record the identification number of the dam of each cow and the number of daughters and their mean performance of each bull. Another method of estimation which requires a second “progeny test” for the old bulls is discussed. A fairly high number of bulls with two progeny tests would be necessary if a precise estimate of genetic progress is desired.
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