Trends in economic traits, halothane sensitivity, blood group and enzyme systems of Swiss Landrace and Large White pigs

Pigs deriving from 150 breeding centres constituting a representative section of elite breeding herds (2496 Swiss Landrace pigs, 587 Swiss Large White pigs) were subjected to blood typing during the period 1981 to 1984. Production traits such as daily gain, feed conversion ratio, lean meat content and meat quality score were available to show the trend in these performance traits since 1978. Field data on the halothane reaction of 14 270 Swiss Landrace (SL) pigs were used to assess the porcine stress syndrome during the period 1978–1983.
In SL pigs the frequency of the alleles H^a, Phi^B and Ada^A decreased significantly, and that of the H^c and Phi^A increased during the period of the study. The frequency of the H^a allele dropped from 0.36 in 1981 to 0.20 in 1984, whereas the H^c allele rose from 0.22 to 0.37. In Swiss Large White (SLW) pigs, on the other hand, the frequency of the H^a allele increased constantly from 0.31 to 0.37 during this period.
An initial frequency of 17.7 % (1978) halothane reactors in SL pigs was lowered to 0.7 % (1982) after five years of halothane testing.
In SL pigs the meat quality scores improved regularly, whereas in SLW pigs it did not change very much. The percentage of PSE animals in the SL breed was reduced from 32.7 % in 1978 to 7.1 % in 1983.
Because the Hal locus is associated with production traits such as meat quality, linkage disequilibria could explain the observed associations between the H and Phi types and production traits.