Allelic incidence in several pig breeds of a missense variant of pig melanocortin-4 receptor (MC4R) gene associated with carcass and productive traits; its relation to IGF2 genotype

MC4R, melanocortin-4 receptor, is involved in feed intake regulation. A mutation in a single base of MC4R, a G/A substitution in position 1426, has been linked to enhanced backfat thickness, average daily gain and daily feed intake. We present in this work a method to diagnose this mutation using real time PCR (RT-PCR) which allows rapid, cheap and reliable analysis of hundreds of samples in just 2 h after DNA extraction. We have used this RT-PCR based assay to study the incidence of the mutation in several pig breeds or crosses (Iberian, Duroc, Pietrain, Large White, Large White × Pietrain) and wild boars. IGF2, insuline like growth factor 2, a gene with well demonstrated effects on carcass composition, of all these animals has also been analyzed and we show, using linkage disequilibrium analysis that both genes are independent. The implications of our results for pig selection toward fatty or lean carcasses are discussed.