Results
Melanocortin-5 Receptor
Melanocortin-5 receptor (MC5R) has been found to be associated with thermoregulation through gland secretion (van der Kraan et al., 1998; Chen et al., 1997) and serves a possible role in lipolysis of adipocytes (Boston, 1999). Kim et al. (1999) mapped porcine MC5R to SSC 6 and detected two single nucleotide polymorphisms within the porcine sequence. Previous analyses have not investigated the association between the porcine MC5R gene and fat deposition, growth or carcass quality traits in pigs.
Results indicate that the MC5R BsaHI PCR-RFLP, developed by Kim et al. (1999) was polymorphic in Berkshire, Duroc, Landrace and Hampshire populations. The frequency of alelle 1 was 0.82. Genotypic frequencies varied within the breeds, however, the homozygote 11-animals were the most frequent (0.75) in the total population.
Total population analysis revealed effects (P<0.05) of MC5R on 10th rib backfat (Table 1), with the 11 and 12-animals being fatter. Similar numerical differences were also noted for the last rib location (P=0.14). Loin muscle area also approached significance for the total population analysis (P=0.10). The results of the individual breed analysis (not shown) revealed differences (P<0.05) between MC5R genotypes with color and Japanese subjective scores, Minolta and Hunter color values, as well as, Instron tenderness for Berkshire; quality index for Hampshires; all backfat measures and intramuscular fat percentage for Landrace.
This MC5R BsaHI PCR-RFLP appears to have its greatest effects on backfat in the total population. Further analysis is needed to fully characterize the differences in meat quality characteristics such as color and intramuscular fat percentage within the breed populations.