Comparison between different procedures to determine the relative importance of the lifetime performance traits in predicting breeding values of Holstein cows [electronic resource].

Includes references.

Data used in this study comprised 2730 lactation records of 850 Holstein cows sired by 316 sires. The Holstein cows belong to a commercial farm. The objective of this work was to determine to what .extent breeding value (BV) is influenced by lifetime variables (Total milk yield at first lactation (TMYJ).Total milk yieid at last lactation(TMYL). 305 milk yield at first lactation (305M1). 305 milk yield at last lactation (305ML), milk per day at productive life (Mday),number of complete lactations (NCL), lifetime days in milk (LDIM),productive life (Plife), age at disposal (CULL) and longevity index (LI, %)) using the stepwise multiple linear regression analysis (SMLR) and partial least squares regression (PLS) procedures. The variables are important for the projection of breeding values (BV) were the variables measured-in-weight (TMY1, MDAY, TMYL, 305M1 and 305ML).The variables measured-in-duration (day or month or lactation) (NCL, U, Cull, Plife and LDIM) have low influence on the BV estimations model. PLS resulted in R! of 0.64 and root mean squares for error) of223. SMLR results were slightly lower R1 of 0.61 with root mean squares for error of231 using the same lifetime variables.

Summary in Arabic.

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