One collected the data from SYMLEK system base about twenty-four hours milk yield, milk composition and somatic cells content in 16 3196 control milkings, from 21 746 cows keeping in 2 158 herds on Pomerania and Kujawy, Poland. One ascertained an increase in twenty-four hours yield and milk composition improvement, following together with an increase of Holstein Fresian (hf) gene share and also of herd production level. This shows on advisability of national cattle improvement by enlargement of hf race gene share, especially in chance of possibility of conditions creation to high production for cow crossbreds. One showed that an increase in twenty-four hours cow yield in following lactations grew together with greater hf race gene share. Together with an increase of somatic cells number in milk followed clear decrease of twenty-four hours yield in each genetic group (the greatest in cow groups with hf race gene share above 50%).

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