Genotype x environment interactions in pig breeding programmes. V. Genetic parameters and sire x herd interaction in commercial fattening.

An experimental progeny test of 107 Dutch Yorkshire AI boars was designed under commercial fattening conditions to estimate genetic parameters and to examine sire x herd interactions under these conditions. Individual records of 8148 crossbred fattening pigs, born on 27 sow herds and fattened on 35 fattening herds, were obtained. The information included daily gain during the fattening period (DGF), carcass weight (CW), carcass weight day−1 of age (CW/A) and scores for backfat thickness (BC) and type (T). Heritability estimates for DGF, CW/A and CW were 0.05, 0.08 and 0.05, respectively, using a model that included a significant (P<0.001) sire x herd interaction, but were somewhat higher if the interaction was excluded. For BC and T the sire x herd interaction was not significant (P>0.05) and a heritability of 0.10 was estimated for both traits. These relatively low heritabilities are probably caused by inadequate performance recording. Commercial fattening data may therefore be of little value for the purposes of genetic improvement. Genetic correlations between sires' progeny in different herds, varied between 0.1 and 0.5 for the growth traits. Non-random mating and preferential treatment are not likely to contribute to the sire x herd interaction in commercial fatttening. In view of the fact that there are so many environmental differences between commercial herds, environment-specific genes are expected to be responsible for the low genetic correlations between herds.