Genetic correlations between purebred and crossbred performances and different environments in pigs from test stations in Lower Saxony

Genetic correlations between genotypes and housing systems for seventeen traits of the complexes fattening, carcass and meat quality were estimated in order to show possible genotype x environment interactions and the degree of accordance between purebred and crossbred performance. Data of 8945 female pigs tested in two test stations of Lower Saxony in the years 2000 to 2005 were analysed. Piétrain purebred and crossbred progenies were kept in two-pig pens, and crossbred progenies were also kept in groups with ten pigs. The crossbred progenies originated from hybrid sows (German Landrace * German Large White). For statistical analysis three animal groups were defined: purebreds in twopig pens, crossbreds in two-pig pens, and crossbreds in groups with ten pigs. Variance components were estimated simultaneously for all three animal groups with an animal model by REML. Statistical models considered the fixed effects month at the beginning of the fattening period within station (fattening), day of slaughtering within station (carcass and meat quality), regression on carcass weight and the random effects of test group and animal.Between the crossbreds of the two housing systems the averaged genetic correlation for all traits is rg = 0,87 (0,51 to 0,99). The mean correlation between purebreds and crossbreds kept in two-pig pens resulted in rg = 0,72 (0,17 to 0,99). Finally, between purebreds and crossbreds kept in groups with ten pigs the mean correlation is rg = 0,63 (0,02 to 0,99). For fattening and carcass traits the estimated correlations are higher than for meat quality traits. Considering the important traits daily gain, meat content and pH1-value cutlet the results do not indicate the existence of genotype x environment interactions between crossbreds in the two different housing systems. Also a wide accordance can be stated between purebreds and crossbreds kept in two-pig pens. The correlations for the combination purebred and crossbred in groups with ten pigs show a good accordance with the exception that the group size influences the daily gain (rg = 0,65). So, for this trait moderate differences in the ranking of the purebred boars can be expected.

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