Abstract
A total number of 2854 lactation records of 699 Friesian cows sired by 80 bulls, during the period from 1985 to 2014 were used in this study to investigate of month and year of calving and parity as fixed factor and sire and dam within sire as random factor; in addition estimate phenotypic and genetic parameters for 305-day milk yield (305-dMY), Lactation period (LP), peak milk yield (PY) and days open (DO); nineteen selection indices (general and reduced) using one phenotypic standard deviation as REV1 and lamont method as REV2. Least square analysis showed significant (P<0.05) effect of genetic and non-genetic factors on all studied traits except the effect of month of calving on 305-dMY. Heritability estimate for 305-dMY, LP, PY and DO were 0.33, 0.07, 0.26 and 0.04, respectively. Phenotypic correlation between each two traits ranged from 0.03 to 1.0; and genetic correlation between each two traits ranged from 0.41 to 0.96; general indices I1 and I11 incorporating 305-dMY, LP, PY and DO was the best (RIH = 0.57) and it is recommended if the selection was exercised; in addition there are high similarity of genetic gains under the two different groups of economic values REV1 and REV2.