Abstract. The aim of the study was to identify non-genetic factors that influence milk
production in dairy cows at the National Center Breeding for Dairy Cattle and Forage (BBPTU
HPT) of Baturraden. The data examined were 1821 production records from 699 dairy cows
that had completed 1-6 lactation. Non-genetic factors studied were season, lactation period,
number of lactation days and age at calving. The effect of non-genetic factors is analyzed by
multiple regression. The results showed that number of days milked had highly significant
effect (P