Impact of crossing system on relative economic weights of traits in purebred pig populations

The relative economic importance of traits was calculated for various crossbreeding systems in pigs. The influence of the following three factors on the relation of standardised and discounted economic weights (SDEW) for reproduction and production traits was investigated (i) the position of breeds in the crossing system, (ii) the use of breed-sex groups for mating in different tiers and (iii) the level of the management input parameters. The SDEW for each trait was calculated as the product of the marginal economic value, the genetic standard deviation and the number of discounted expressions. The ratio of SDEW for reproduction traits to SDEW for production traits was from 3 : 1 to 3.7 : 1 which is about twice the value of the corresponding ratio of undiscounted standardized economic weights (1.7 : 1). There were small differences in the ratio of standardized economic weights for number born alive and average daily gain (SDEWR) between males and females used for mating in the same tiers within a given crossing system (loss than 1 %). In each breed-sex group, there were significant differences in the SDEWR (up to 24%) dependent on the use of this group for mating in different tiers within a given crossing system or in different crossing systems. This means that clients at multiplier and commercial levels should rank the genetic merit of their breeding stock differently from that of a common breeding objective. In crossing systems with two dam breeds without reciprocal crossing, the SDEWR was higher in the breed used in granddam position than in the breed used in grandsire position (about 20% under Czech conditions). Changes in the management parameters had only a minor impact on the SDEWR.