Proportional, regression and modified regression correction factors for prediction of 305-days milk and fat yield of Black-White and Holstein-Friesian cows and crosses based on short-term cumulated yields were calculated. Cumulation from 1 to 10 and from 10 to 1 month of lactation was considered. There are different correction factors for cows of different breeds and crosses and for different traits.
Proportional correction factors for prediction 305-days milk and fat yields based on short-term cumulated yields dependend on production level, calving season and length of calving period for Black-White and Holstein-Friesian cows and crosses are estimated. Production level affected to all correction factors for days of calving, but calving period and season of calving affected to correction factors of initial and final months of lactation only.