Genomweite Effekte auf Zuchtwerte abhangig vom Laktationsabschnitt in Holstein Friesians

Many quantitative traits such as weight gain and lactation yields show a phenotypical time-dependency. Milk production traits of dairy cows have been thoroughly analysed over the last century and their development characterised with lactation curve models. Previous studies described that variances and direct genetic effects are also time-dependent. Thus, the DGAT1 gene was shown to have a decreasing effect on milk and protein yield with a simultaneous increase of fat yield and fat and protein content (i. a. Thaller et al. 2013), however, this effect is not pronounced during the first 40 lactation days or even reversed for milk and protein yield (Strucken et al. 2011). The first weeks of lactation are especially critical for high production dairy cows. During this time, an energy deficit manifests due to the sudden and fast increasing milk production and a physiologically restricted energy intake. The aim of this study was to characterize the underlying genetic effects for milk production traits in early lactation and to compare these results with cumulative 305-day records.