Browsing by Author "Mikkola, Lea"

In the last two decades, a variety of studies have introduced the idea that there are significant differences between levels of variance components and heritabilities, between breeds of beef cattle. In this study the following carcass traits were observed for these differences: slaughter weight, carcass class and carcass fatness. The breeds used for this evaluation were hereford, charolais, aberdeen angus, limousin, simmental and highland cattle. Cattle breeds may differ by their physiological traits and breeds are often divided into groups by their original continents. One of the objectives of this study was to analyse the level of such differences and their impact on the genetic improvement of carcass traits. To successfully define these matters it is essential to determine the genetic parameters of carcass traits for each breed separately. After assessing the levels of genetic parameters for each breed in question, the significance of the differences between genetic variances was evaluated. Two models were compared: an unconstrained model, in which the breeds were seen as different traits, with their own variances and a constrained model in which the breeds were also as separate traits but with one joint variance. The results suggest that the unconstrained model is to be preferred over the constrained model. The differences between the levels of variances and heritabilities were apparent between breeds. For highland cattle the results were only indicative due to the limited amount of data acquired. These differences between the breeds’ genetic parameters may affect the prediction of breeding values severely. Therefore, it may be noted in the light of this study that the best breeding values might be obtained by assessing the breeds separately.