ESTIMATION OF CROSSBREEDING PARAMETERS FO R FERTILITY TRAITS IN DAIRY-CATTLE

In the sixties breeding of the German Black Pied Dairy Cattle (SMR) ha s been initiated in East Germany by systematic crossing Holstein-Fries ians and Jersey with the local Black Pied Cattle. First to fourth lact ation records of about 820,000 (1st lactation), 650,000 (2nd lactation ), 500,000 (3rd lactation) and 340,000 (4th lactation) purebred and cr ossbred cows, that had calved For the first time between the years 197 0 and 1984, were included in the investigation. Traits under analysis were calving interval, days open and number of inseminations per servi ce period. The large number of purebred (3) and crossbred (68) genetic groups made it possible to estimate epistatic effects. Models used we re derived by DICKERSON (1969), KINGHORNS (1987), GROSSHANS et al. (19 94) and WOLF et al. (1995). Holstein-Friesians showed significant posi tive additive-genetic effects on calving interval in the range from 8, 67 to 16,21 days and similar effects for days open. Also the number of inseminations were significantly increased by the additive-genetic ef fect of Holstein-Friesians. For the additive-genetic effect of Jerseys a significant reduction of the calving interval in the first lactatio n could be found, whereas in the fourth lactation a significant prolon gation of days open was evident. Heterosis effects in two-breed-combin ations with Jerseys showed the tendency to reduce calving interval and days open, whereas the two-breed-combination Holstein-Friesian by Bla ck Pied Cattle increased the calving interval. Epistatic effects influ ence all fertility traits analysed significantly. Two breed combinatio ns with Holstein-Friesians showed recombination and additive x additiv e effects significantly reducing the calving interval in some lactatio ns, but the days open in most lactations. Jersey by Black Pied Cattle crossbreds reduced calving interval in the first lactation through the ir recombination and additive x additive effects, but in the higher la ctations the sign of these effects reversed. Other epistatic effects s eemed not of higher importance.