What can be gained by the BLUP procedure under various circumstances?
and NW within each parity are very high, from 0.7 to 1. Genetic correlations between data of consecutive parities seem to be high, excepting those including the first litter, which go from 0.7 with the second to 0 with the fourth (for NB and NA). So it appears that data of first parity are a poor enough information about the genetic value of sows ; on another hand, taking into account the genetic correlation between parities could improve the efficiency of selection on litter size. Heterosis and maternal effects on daily gain, feed conversion ratio and carcass traits were investigated in the pig crossbreeding experiment. Three breeds of pigs were used : Large White, Dutch Landrace, and Swedish Landrace. Nine genetically different pig groups of purebreds and crossbreds had been examined. General heterosis effects were small and nonsignificant. Comparisons between pure breeds show small differences with Dutch Landrace to some extent exceeded two other breeds. Significant specific heterosis effects were found for daily gain, feed conversion ratio and fat thickness at shoulder. Average difference in reciprocal crosses or general maternal effects were significant for daily gain and feed conversion. Specific maternal effects were significant for all characters studied, with exception for carcass length. Definition and development of breeding programs require data as a basis of analysis. A micro computer system is described which supports and carries out the routine calculations that have to be done in a breeding program. All data handled are stored on floppy discs or cassettes. Input is checked for plausibility. Data transmission to a central computer is via a direct link between the micro computer and the host. As a by-product of index calculation for auction boars in Northern Germany data on 23 000 boars have been collected in 1980, which comprises the total male population on sale in this region and 40 p. 100 of all boars sold in the Federal Republic of Germany.