Expected reliability of cow's breeding value for average life-time milk production
2001
Pribyl, J. | Pribylova, J. (Vyzkumny Ustav Zivocisne Vyroby, Prague (Czech Republic))
The aim of this study was to determine the reliability of breeding value estimation of cows for average lifetime milk yield. The animal model method was used. The following parameters were taken into account: the first or the first three lactations, number of contemporaries within herd-year-season (HYS, 1 to 15), degree of relationship between contemporaries, number of half-sisters (10 to 100) and relationship with the father or full relationship over 3 generations of ancestors. Two levels of heritability are used (0.32 and 0.21). Within-herd variability changed with the increasing magnitude of HYS. The reliability of breeding value estimation is r**2 = 0.535. It is by 12 % higher than with the first lactation only. Reliability increases if the contemporaries are not related. Reliability also increases with the increasing number of contemporaries within HYS. When reaching 5 contemporaries, further increase in reliability is low. Reliability is influenced by the number of half-sisters. With 50 half-sisters and more, at least a 90 % level of maximum possible reliability is attained, practically regardless of the number of contemporaries within the herd.
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