The objective of this study was to determine relationships between sire effect, milk production in young cows, their performance in subsequent lactations, fertility, conformation and productive longevity. A total of 1724 cows that first calved between 2003 and 2005 were analyzed during 4475 lactations. The cows were kept in 10 barns located in the Provinces of Pomerania and West Pomerania, Poland. The analysis covered 1085 daughters of 145 local Polish Holstein-Friesian (PHF) sires and 639 daughters of 128 imported Holstein-Friesian (HF) sires, including 437 cows culled after the first lactation, 445 cows culled after the second lactation and 140 long-lived cows. Research has shown that among first-calf heifers and the second lactation cows more than 55% of daughters of imported bulls and about 48.75% of daughters of domestic bulls were culled. Essentially higher results of sort ratings concerning the overall appearance, body conformation, udder quality and frame size, efficiency of milk and its components were acquired after the imported bulls. High milk production levels, exceeding 8000 kg of milk in the first and second lactation, had an adverse effect on the productive life of cows. A correlation between milk production of milk cows and their productive longevity was proved as evidenced by the fact that cows which were used for at least five lactations produced less milk and its components as the first-calf heifers than cows which were scrapped later.
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