IMPORTANCE OF THE TRAITS IN 2-STAGE SELEC TION INDEX

Two-stage selection index has been made up for the bulls of Czech Pied cattle. Each trait of selection index and of the aggregate genotype p articipates in the level of genetic gain to a larger or smaller extent , and this determines its importance. This paper is a follow-up of the article written by Kratochvilova et al. (1994). The calculation was b ased on the paper by Cunningham (1977), which describes computer progr am SELIND for calculation of two-stage selection indexes, as well as r elationships for calculation of the importance of the traits in select ion index, correlations between the traits in the aggregate genotype a nd selection index, and percentage of i-th trait with respect to total genetic gain. The results in Tab. III show dial a decrease in the gen etic gain from selection would be largest if these traits of selection index for 1st and 2nd stage of selection were omitted: 1st stage weig ht gain during test weight gain from birth to selection 2nd stage weig ht gain during lest milk production Tab. IV shows mutual correlations between the traits Y in the aggregated genotype and selection indexes. It is apparent from the calculated correlations that in the 1st stage there is a high positive correlation between index and weight gain (r = 0.68) and a high negative correlation (r = -0.61) between index and feed conversion. In the 2nd stage there was a marked increase in the correlations between index and genotype traits. The highest positive c orrelation was found between index and cow weight (r = 0.61), between index and weight gain (r = 0.56) while the highest negative correlatio n was between index and feed conversion (r = -0.54). It follows from t he above data that when the values of selection index am increasing, t hose traits of the aggregate genotype are increasing which are in posi tive correlation with the index, and on the contrary the values of the traits with negative correlations in the genotype are decreasing whil e the index value is rising. The only traits that cannot be influenced are those with al most zero correlations with the index. They am repr oductive figures, length of cow efficiency and mastitis. Bat these tra its can also influence some productive traits to a certain extent on t he basis of positive correlations, therefore they have their economic value, ensuing importance in the aggregate genotype and selection inde x. Determination of the percentual sham of each i-th trait in the tota l genetic gain (Tab. V) shows that this percentage was highest in the first stage in feed conversion (39.02%), followed by the percentage of main lean cuts (22.75%) and weight gain (20.84%). On the other hand i n the 2nd stage milk amount (50.63%) and feed conversion (24.55%) had the highest percentages showing their participation in the total genet ic gain.