Analyse of dairy performance traits mutability of cows-daughters after red-factor bulls

The researches were done basis on analyse of control performance evaluation of 62 cows after red-white cows and 3 red-factor black-white bulls mainten ance at modern dairy cattle farm in south-west Poland. There was found stat istically important differences (P less than or equal to 0,05; P less than or equal to 0,01) in production of: milk, fat, protein, dry matter and milk in FCM during first 305 days lactation. Bulls who have progeny with high level of dairy performance and low changea bility of this trait should be prefer in dairy cattle reproduction. Thanks to selection increasing dairy performance it is possible to increase proportion between protein and fat content and decrease differences betwee n those components at the cost of lowering fat content and small decrease o f protein content in milk. Obtained results could be useful in breed work upon transformation of home dairy cattle in new - more dairy type.