The estimation of breeding value is assessed with an error minimized by the test set-up, appropriate production recording and methodology of data evaluation. Reliability of the estimated constants is determined by inversion of left hand side matrix of the system (Searle, 1971 ; Henderson, 1984). The reliability is contained in breeding value. Thereby, it is of less importance for the actual animal selection. The main use of this coefficient is in design of the milk recording collection and the procedure for the data evaluation to minimize the expected error. The variability of breeding value and production deviation from contemporaries was described by Přibyl (1986). The formula for the error of breeding value estimation depending on the number of tested bulls and number of herds was derived by Herrendörfer et al. (1974). Effect of the relationship among the animals on reliability of breeding value was studied by Mostager (1970 and 1971). The influence of the HYS size, number of non-related contemporaries and the incidence of direct comparison of tested animals within the HYS at a different level of heritability were studied by Tosh, Wilton (1994). Schmitz et al. (1991) showed, that the prolongation of HYS leads to increase of uncontrolled variability. Cow selection is aimed at average life-time milk production. Prediction of the breeding value for the average life-time production according to the known first lactations can be attained only with partial reliability (Přibyl and Přibylová, 2001). The goal of this study was to estimate the expected reliability of breeding value for average life-time milk production of the cow depending on the number of contemporaries within HYS and a variable number of paternal half-sisters.  

J. Poibyl, J. Poibylova

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 2002. Session 1, , 1.61, 2002
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