Relationships between blood groups, isozymes and halothane reaction in pigs from a selection experiment

German Landrace pigs (n = 1500) were halothane-tested and blood samples were taken for the determination of A-O and H blood types as well as for the determination of PHI and 6-PGD isozymes. The pigs originated from two generations (7th and 8th) of a selection experiment 'selection for activity of NADPH-generating enzymes in backfat of pigs'. The selection lines are E-, E+ (selection for low and high enzyme activity), U- (selection for low ultrasonic backfat thickness) and K (control). Preliminary results show an average proportion of halothane-susceptible animals of 49%. The frequencies of halothane-positive pigs amount to 60%, 46%, 70% and 30% in lines E-, E+, U- and K, respectively. The investigation shows a non-random combination of the marker genes caused by linkage disequilibrium, especially in line E-. Recombination frequencies between the loci vary from 0% to 18%.