A Comparison of Different Selection Indices for Genetic Improvement of Some Dairy Milk Traits in Holstein Friesian Cows in Turkey

Abstract

Atil, H., Khattab, A.S. and Gevrekci, Y. 2005. A comparison of different selection indices for genetic improvement of some dairy milk traits in Holstein Friesian cows in Turkey. J. Appl. Anim. Res., 27: 117–120. A total of 1680 first lactation records of Holstein Friesian cows sired by 206 bulls maintained at five herds in Turkey were used to estimate phenotypic and genetic parameters for 305 day milk yield (305 dMY), lactation period (LP) and age at first calving (AFC). Data were analysed using Multiple Trait Derivative Free Restricted Maximum Likelihood (MTDFREML). The model included the fixed effects of herd, season and year of calving and parity, AFC as a covariate and individual and residual as random effects. Genetic correlations between 305 dMY and AFC; and LP and AFC were 0.90 and −0.95, respectively. Phenotypic correlations among all traits studied were generally similar to the corresponding genetic correlations. Index I1 incorporating 305 dMY, LP and AFC was the best (RIH=0.75). It is recommended that selection should be exercised at the end of the first lactation.