INVESTIGATIONS ABOUT THE LENGTH OF PRODUC TIVE LIFE OF BLACK-AND-WHITE CATTLE

The results of yield development and departure within two milk product ion enterprises over a time of 10 years show that throughout a high yi eld productive availability and a good length of productive life may b e compatible. A high but not highest first lactation yield is an essen tial assumtion. In simulate experiments the shifting of selection poin t of time between each lactations at selection of the 75% best animals (accordingly the practical selection of productive) doesn't lead to a change of the cumulative yield of the animals. At selection of the 5% best animals (accordingly the selection of bullmothers and donors) th e shifting of selection point of time from the first to the third lact ation leads to a higher cumulative yield of 16% in 5 lactations.