Stability to leukosis of cows of different genotypes in the Southern Urals

It is established that on the unfavourable farm (with high level of leukosis) the amount on infected cows with the virus of leucosis varies among the studied cattle lines. In cows of Don Juan 1347 line it was 80 per cent, Wis Ideal 933122 - 65, 3 per cent, Reflection Sovering 198998 - 43, 2 per cent, Poseidon 239 - 41, 2 per cent. The lovest degree of infection with leukosis virus was among the cows of Annas Adema 130587 line - 25 per cent. Most of RID-positive animals were at the age of 4 and 5.