We performed a genome-wide QTL scan for production traits in a line cross between Duroc and Pietrain breeds of pigs, which included 585 F(2) progeny produced from 31 full-sib families genotyped with 106 informative microsatellites. A linkage map covering all 18 autosomes and spanning 1987 Kosambi cM was constructed. Thirty-five phenotypic traits including body weight, growth, carcass composition and meat quality traits were analysed using least square regression interval mapping. Twenty-four QTL exceeded the genome-wide significance threshold, while 47 QTL reached the suggestive threshold. These QTL were located at 28 genomic regions on 16 autosomal chromosomes and QTL in 11 regions were significant at the genome-wide level. A QTL affecting pH value in loin was detected on SSC1 between marker-interval S0312-S0113 with strong statistical support (P < 3.0 x 10(-14)); this QTL was also associated with meat colour and conductivity. QTL for carcass composition and average daily gain was also found on SSC1, suggesting multiple QTL. Seventeen genomic segments had only a single QTL that reached at least suggestive significance. Forty QTL exhibited additive inheritance whereas 31 QTL showed (over-) dominance effects. Two QTL for trait backfat thickness were detected on SSC2; a significant paternal effect was found for a QTL in the IGF2 region while another QTL in the middle of SSC2 showed Mendelian expression.

The amount and distribution of water inside the meat has a considerable influence on its properties. High losses of fluid in the form of drip may affect financial output, nutritional value, consumer appeal and/or technological properties of porcine meat. Therefore, a deeper insight into the traits water-holding capacity (WHC) and drip is favourable on behalf of producers, industry and consumers. Similar to most meat quality traits, WHC and drip loss (DRIP) are moderately heritable. The genetic correlation between these two traits is high. Correlation to other meat quality traits, such as pH value, cooking loss, reflectance, etc. is existent as predictable. Two major genes are known, RYR1 on chromosome 6 and RN on chromosome 15, to influence meat quality in general and WHC in particular. Furthermore, a number of candidate genes exist, e.g. phosphoglycerate mutase 2. Within the variety of quantitative trait loci (QTL) experiments, a number of QTL have been identified. QTL for DRIP and/or WHC have been found on chromosome 1, 2, 4, 5, 6, 11, 13, 14, 15, 18; for cooking loss on 7, 14 and18, and for pH value on nearly all chromosomes. Recently, a QTL study for meat quality and body composition traits in a Duroc-Pietrain (DUPI) resource population has been conducted at the University of Bonn, Germany. Four QTL for DRIP were identified on chromosomes 2, 3, 5 and 18. The QTL regions are in agreement with previously published QTL for this and other related traits. Further research and finemapping has begun and candidate genes located within the QTL regions are currently under investigation. Combination and comparison of results should lead to deeper insights in the genetic background of meat quality and DRIP.