Genotype × Environment interactions in pig breeding programmes. II. Environmental effects and genetic parameters in central test

Abstract

Environmental effects were investigated and genetic parameters estimated in central test results from Dutch Landrance and Dutch Yorkshire pigs, tested on two stations under a restricted feeding regime. To investigate the environmental effects within test stations, different definitions of environmental effects were included separately in models for analysis of variance. Batch effects were significant ( P < 0.001) for daily gain and feed conversion ratio, and explained 7–12% of the variance. Backfat measurements and ham + loin percentage were significantly ( P < 0.05) influenced by month effects. Indications for an optimal environmental classification were shown only for daily gain and feed conversion ratio. For the carcass characteristics no balance could be found between chance and environmental fluctuations. The estimated heritabilities for daily gain, feed conversion ratio and ultrasonic backfatàt thickness were 0.18, 0.21 and 0.28, respectively, if averaged over the two breeds, and were lower than those reported in the literature for pigs on restricted feeding. A different genetic structure (only A.I. data were used) and the chosen definition of environmental effects may have contributed to these differences. The differences between the two breeds in heritability, especially for ham + loin percentage (h 2 = 0.34 for Dutch Landrace and h 2 = 0.75 for Dutch Yorkshire), may be the result of the selection against halothane-positive animals in the first breed.