A Comparison of Different Methods of Estimating Sire Transmitting Ability of Some Milk Traits in a Herd of Holstein Friesian

Abstract

A total of 1931 normal first lactation records of Holstein Friesian cows kept at Dena Farm in Egypt during the period from 1987 to 1994 were used to estimate phenotypic and genetic parameters for 90 and 305 day milk yield (dMY) and lactation period (LP). In addition, 76 bulls with at least ten daughters were used to compare three methods of sire transmitting ability. A least squares analysis of variance show significant effect of month and year of calving and age at first calving for different traits studied, except the effect of age at first calving on LP. Heritability estimates for 90 and 305 dMY and LP were 0.39±0.08, 0.27±0.07 and 0.14±0.05, respectively. Genetic and phenotypic correlations between different traits were positive and significant. Sires with at least ten daughters were evaluated by best linear unbiased prediction, least squares means and regression of the future daughters mean on the present daughters mean. The product moment correlations between different traits studied were positive and high (-0.96).