Impact of selection of dual purpose cattle on secondary traits

The selection of dual purpose cattle is simulated by selection indices. It includes milk (amount of milk, milk protein) and beef production (dairy gai n, valuable meat cuts, growth capacity feed conversion) and secondary trait s (fertility, longevity, mastitis, calving difficulty). Partial breeding va lues for traits are combined into selection indices. Economic values of 1, 1.5, 2 and 4 multiples of results of the profit function are assigned to se condary traits in the indices. In the case of basic variant, the genetic ga in of milk production is 58 kg and effects of selection on milk and beef pr oduction and secondary traits are at a ratio 81 : 20 :-1. The most importan t traits in the indices are amount of milk, feed conversion, milk protein c ontent and daily gain. Most secondary traits show worse values. In the case of 1.5 multiple overvaluation of secondary traits, the genetic gain is 51 kg of milk and ratios of selection are 72 : 19 : 9. In the case of 2 multip le overvaluation the genetic gain of milk is 43 kg and ratios of effects fo r groups of traits are 59 : 18 : 23. In the case of 4 multiple overvaluatio n the genetic gain is 15 kg and the ratios are 17 : 10 : 73. With overvalua tion of secondary traits, the ratio of milk to beef production is decreased .