Changes in the genetic pool and milk performance of the primiparous cow population in Poland

The study analysed trends in the genetic pool and production traits of Poland's population of Black-And-White (BW, n = 166061 heads) and Red-and-White (RW, n = 8834 heads) primiparous cows between 2000-2001. The genetic pool of dairy cows in Poland has undergone change due to extensive cross breeding with HF cattle. In 2001, the percentage of pure-bred (without HF blood) primiparous cows of BW and RW cattle was 8,42 and 6,15%, respectively. At the same time, hybrids with various shares of HF blood accounted for, 91,58 and 93,85% of the populations of BW and RW cattle. The above data indicates that, compared. to 2000, the share of pure-bred (without HF blood) primiparous cows changed respectively by +0,71 for BW and by -1,93% for RW cattle. The highest reduction in cow numbers was observed for both BW and RW cattle in the groups hg a low share of HF blood (<25 and 26-50%). A increase in numbers was noted in the groups of RW cattle with 51-75 and 76-99% share of HF blood, respectively: +3,44 and +5,86%; while in BW cattle the respective results were: -0,75 and +4,78%. The twice as intensive changes in the increasing share of HF blood in RW cattle compared to BW cattle did not have the same impact on production. The average yearly production gain of BW cattle (+296 kg milk, +12,1 kg fat, +10,0 kg protein, 0,0% fat and +0,01% milk protein) was twice the production gain in RW cattle (+142 kg milk, +5,3 kg-fat, +3,6 kg protein, -0,01% fat and -0,02% protein in milk). The limited improvement observed in breeding goals (milk yield and composition) in RW, cattle was probably caused by the use of low value sires in the breeding programme.