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Summary A considerable number of fatness QTL have been identified in growing pigs, but there is a lack of knowledge about the genetic architecture of this trait in gilts and sows. We have performed a genome scan, in 255 Iberian × Meishan F2 sows, for backfat thickness (BF) at 150 (BF150) and 210 (BF210) days of age, 30 days after conception (BF30) and 7-10 days before farrowing (BFbf). We have found one BF150 QTL in SSC6 (120 cM) that was highly significant ( P < 0.001) at the chromosome-wide level and suggestive at the genome-wide level ( P < 0.1). Ten additional chromosome-wide significant QTL were found for sow BF150 (SSC1, SSC13), BF210 (SSC6, SSC8, SSC15), BF30 (SSC5, SSC6) and BFbf (SSC1, SSC6, SSC13). The location of several of the BF QTL varied depending on the growing and reproductive status of the sow, suggesting that part of these genetic effects may have a temporal pattern of phenotypic expression. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate chromosomal regions affecting the number of teats in pigs and possible epistatic interactions between the identified quantitative trait loci (QTL). An experimental F2 cross between Iberian and Chinese Meishan lines was used for this purpose. A genomic scan was conducted with 117 markers covering the 18 porcine autosomes. Linkage analyses were performed by interval mapping using an animal model to estimate QTL and additive polygenic effects. Complementary analyses with models fitting two QTL were also carried out. The results showed three genomewide significant QTL mapping on chromosomes 5, 10 and 12, whose joint action control up to 30% of the phenotypic variance of the trait. Meishan alleles had a positive additive effect on teat number, and a positive-additive × additive-epistatic interaction was detected between QTL on chromosomes 10 and 12. [ABSTRACT FROM AUTHOR]