Association of the melanocortin-4 receptor (MC4R) with feed intake, growth, fatness and carcass composition in pigs raised in Poland. 
The melanocortin-4 receptor (MC4R) is involved in feed intake regulation.  A missense mutation G/A in position 1426, which causes Asp-Asn substitution at position 298 in the MC4R gene has been associated with feed intake, fatness and growth, however published results of its effect are inconsistent.  In our study we evaluated an effect of missense mutations on carcass composition, growth traits and meat quality in 1191 gilts of five breeds: Polish Large White, Polish Landrace, Puławska, Pietrain and Duroc.  G/A 1426 MC4R mutations were genotyped using a 7500 Real-Time PCR System (Applied Biosystem).  Our observations confirm that the G allele is frequent in breeds selected for lean meat content (Pietrain - 92.4%) and rare in breed with a fat carcass (Duroc - 31.5%), which has been previously reported.  Our study revealed that the A allele was associated with increased daily feed intake (AA - 2.51kg; GG - 2.31kg in the Puławska breed, P<0.05), daily gain and backfat thickness (AA - 1.67cm, GG - 1.52cm in PL, P<0.01) and decreased lean meat content (total weight of ham was 0.5kg greater in G/G than in A/A Puławska animals).  We obtained an unexpected result for IMF: higher percentage of IMF was observed in the G/G genotype.