The effects of leptin receptor (LEPR) and melanocortin-4 receptor (MC4R) polymorphisms on fat content, fat distribution and fat composition in a Duroc × Landrace/Large White cross

The effects of mutations LEPR c.1987C>T and MC4R c.1426G>A on leptin receptor and melanocortin receptor genes, which are involved in regulating appetite, have been studied in a Duroc × Landrace/Large White cross. To the best of our knowledge, this is the first report of the presence of LEPR c.1987C>T effects outside the Iberian breed or crosses of Iberian with other breeds. Both mutations modify several traits related to adipose tissue content. LEPR TT pigs have a lower percentage of joints rich in muscle tissue and a higher percentage of joints rich in adipose tissue in the carcass (5.8% lighter loins, 6.0% heavier lard) than LEPR CC pigs. LEPR TT pigs also have a greater adipose tissue content in their hams (8.0%) and shoulders (24%) than LEPR CC homozygous pigs. They also have larger backfat thickness values (between 1.5 and 7.5 mm depending on anatomical location). LEPR TT pigs show a clear increase in saturated fatty acid content at the expense of monounsaturated and polyunsaturated content when compared to LEPR CC pigs. MC4R GG pigs have a higher percentage of joints rich in muscle tissue and a lower percentage of joins rich in adipose tissue in the carcass (6.3% heavier loins and 4.7% lighter lard), lower fat cover and higher muscle fraction in hams (9.3% and 3.4%, respectively), and a larger fat content in B. femoris (12.2%) and in whole ham muscle mass (8.6%) than MC4R AA pigs. Whereas most effects of both mutations can be explained by an increase in feed intake, the strong effects of LEPR c.1987C>T on saturated fatty acid content in several anatomical locations are probably due to the local effect of a compromised leptin signaling system. The consequences of selecting these mutations for cured meat production are discussed.