A melanocortin-4 receptor (MC4R) polymorphism is associated with performance traits in divergently selected large white pig populations

The melanocortin-4 receptor (MC4R) has a vital role in the control of energy balance and the genetic basis of obesity. A polymorphism, which results in the replacement of aspartic acid with asparagine at position 298 of the porcine MC4R gene, within the seventh transmembrane domain, has previously been described. In the current study, allele frequencies for this Asp298Asn polymorphism were investigated in lines of Large White pigs which had been divergently selected for seven generations based on lean food conversion (LFC), lean growth with ad libitum feeding (LGA), lean growth with restricted feeding (LGS) and daily feed intake (DFI). The association of the Asp298Asn polymorphism with performance traits in these lines was assessed. The frequency of Asp298 was higher (P < 0.001) in the LFC high line (0.48) than the low line (0.00), while the frequency of Asn298 was higher (P < 0.01) in the LGA high line (0.22) than the low line (0.04). When analysed across all lines, the Asp298Asn polymorphism was significantly associated with ultrasonic backfat depth, average daily gain and daily feed intake (P < 0.05). Asp298 homozygous animals had mean values of 13.3 mm, 733 g and 1933 g for backfat, average daily gain and daily feed intake respectively, compared with 14.7 mm, 805 g and 2098 g for Asn298 homozygotes. Therefore, the data support a role for the MC4R Asp298Asn polymorphism in the genetic basis of economically important traits in Large White pigs.