Weight coefficients of lactations in animal model
2001
Pribyl, J. | Pribylova, J. (Vyzkumny Ustav Zivocisne Vyroby, Prague-Uhrineves (Czech Republic))
Dairy cattle are selected for an average of lifetime milk production. Breeding value is estimated using MT-AM (multi-trait animal model, each lactation as separate trait). For each order of lactation discounted interest values are calculated, dependent on age structure and calving interval. The first lactation out of 10 lactations has a relative importance of the whole number of lactations. In the case of a 0 % interest rate it is 0.34, with a 5 % interest rate it is 0.37 and with a 10 % interest rate it is 0.40. The average lifetime production is predicted on the basis of the early lactations. If the interest rate is 5 %, the breeding value for the first lactation will predict the average lifetime production with reliability over 0.90, breeding values for the first two lactations with reliability over 0.98 and for the first three lactations with reliability over 0.99. The age structure have not a great influence on the reliability of prediction. Optimal weight in the index for partial breeding values, in case of the first lactation only, is approximately 1. In case of the first two lactations it is approximately 0.34 and 0.63, in case of the first three lactations it is 0.31, 0.11 and 0.52. If all the three lactations in the index have the same weight, i.e. 0.33, 0.33 and 0.33, the lifetime average production is predicted practically with equal reliability as in the optimal index. It is caused by high genetic correlations between lactations.
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