A whole-genome scan for quantitative trait loci affecting teat number in pigs

A whole-genome scan was conducted using 132 microsatellite markers to ident ify chromosomal regions that have an effect on teat number. For this purpos e, an experimental cross between Chinese Meishan pigs and five commercial D utch pig lines was used. Linkage analyses were performed using interval map ping by regression under line cross models including a test for imprinting effects. The whole-genome scan revealed highly significant evidence for thr ee quantitative trait loci (QTL) affecting teat number, of which two were i mprinted. Paternally expressed (i.e.., maternally imprinted) QTL were found on chromosomes 2 and 12. A Mendelian expressed QTL was found on chromosome 10. The estimated additive effects showed that, for the QTL on chromosomes 10 and 12, the Meishan allele had a positive effect on teat number, but, f or the QTL on chromosome 2, the Meishan allele had a negative effect on tea t number. This study shows that imprinting may play an important role in th e expression of teat number.