RELATIONSHIP BETWEEN DAILY MILK-YIELD AND PERSISTENCY OF HUNGARIAN HOLSTEIN-FRIESIAN CATTLE THROUGH SELECTION INDEX AND SUBINDICES

Maximum likelihood procedures were used for the analysis of relationsh ips between persistency and daily milk yield performance. Genetic and phenotypic (co)variances were generated from this analysis to construc t full and reduced selection indices, selection subindices and reduced selection subindices. The structure of the data were half-sib familie s of 281 sire groups, lactation records in each group ranged between 1 2-24 records. Expected genetic gain in daily milk yield by selection s ubindices was similar to the corresponding value calculated by selecti on index, so the breeder can use selection subindices in the breeding program to improve the daily milk yield. Contribution of persistency t o the improvement in daily milk yield was higher by the subindex than the selection index. The highest improvement of persistency was associ ated with the maximum improvement in daily milk yield per lactation an d per calving interval and was achieved by the selection index which i nvolved all these traits.