A total of 598 first lactation records of Friesian cows progeny of 30 sires and
535 dams were used in this study. Analysis was carried out using Maximum
Likelihood procedures with the model used including month and year of calving as
fixed effects and sires as random effects. The estimates of phenotypic and genotypic variances and co variances of, 305
day milk yield, 305 day fat yield, 305 day protein yield, calving interval and age at first
calving and their relative economic values derived by two methods were used for
constructing selection indices, method 1 ,actual relative economic V alues (REV( 1) and
method 2,relative weights(REV(2)). Heritability estimates were 0.3i, 0.12, 0.17, 0.19
and 0.44, respectively. Genetic correlations between milk traits were high, positive
and significant (p < 0.01) ranging from 0.85 to 1.00 and their corresponding
phenotypic correlations from 0.60 to 0.97. Twenty-six selection indices for each method of relative economic value
derivation (REV) were constructed. The selection index 11A or 1₁s which in corporated
305 days milk yield, 305days protein yield,calving interval and age at first calving, was
the best (had the highest accuracy (RIH ) and relative efficiency values) and were
recommended, if the selection was exercised at the end of the first lactation. Rank
correlation coefficient between the ranking of 598 Friesian cows !;ty the both methods
of relative economic valus was 0.95 . thus ,the second method of relative economic
values was recommended for ease of calculation.