Single-trait (SAM) and multi-trait (MAM) animal model were compared using
the dal\) of 9().day (M90) and 305-days- (M305) milk yield of 985 of Holstein-Friesian
cows daughters of 104 sires and 985 dams in Egypt. Data included 985 first lactation
records. Total number was 5M2 for all lactations. Animal model in both single- and
multi· trait. contailled season. year of calving. classes of age at calving and days open
as frxed effects and animal and residual as random effects. The variablity in predicted breeding value, PBV (i.e., range from maximum -
mfnmum) was large for MAM in first lactation. however, the reverse trend was found
in all lactations (i.e .• ranges of PBV in SAM was larger than the estimates from
MAM). Using MAM decreased the standard error of prediction (SEP) and
consequently the accuracy (rn) increased . Closeness between rpM and rs of both
SAM and MAM prove thai any model may be effective in the evaluation of sires.
dams and cows. Using records of all lactation reduced SEP in both SAM and MAM
procedures than those of first lactation only. Inerasing accuracy with all lactations was
maltedly pronounced when compared with the first lactation. Increasing information
from all lactations has a direct effect toward increasing the accuracy (rTI) of the all
lactaion than using only first ladation. Oisclosness between correlations (rPM & rs) of
PBV and ranks in first and alliactalions, indicate that the sires, dams and cows were
reran ked when using firsllactation and all lactation records. Part-lactation yields (MOO) in both first and alilactalion records proved 10 be
a good parameter in estimating sire genetic values without complications and would
also afford an opportunity for a faster return for sires. Reduction in sires, dams and
COWS SEP by using MOO compared with M305 using either SAM or MAM provided a
considerable potenti;lll for rapid genetic progress through sire selection, (l.e. there is a
considerable polientlal for improving milk production through selection of bull or bull·
dam's of Holstein population).