The objective of this study was to evaluate an association between the polymorphism of the porcine pituitary-specific transcription factor gene (POU1F1, previously called PIT1) and carcass quality in F2 animals (grandparents: Zlotnicka Spotted boars and Polish Large White sows) being a part of experimental material prepared for a QTL mapping project. The analysis covered a total of 188 F2 offspring of 13 males and 67 females (F1 generation). The RsaI PCR/RFLP polymorphism of the POU1F1 gene was identified and the least squares method was used to evaluate the significance of its effect on the value of carcass quality traits. Three POU1F1/RsaI genotypes were identified in F2 porkers: EE (n=32), EF (n=68) and FF (n=88). Twenty-four carcass quality traits were measured after 24 h of cooling. The POU1F1/RsaI genotype proved to have a significant effect on the following traits: weight of ham bone and bacon including ribs, fat thickness at the lower back (point K3), over the loin, and average fat thickness (mean of five measurements). These results confirm that the POU1F1 gene may be linked to the gene/genes affecting fat deposition in the pig carcass. Moreover, pigs with the EE genotype had a greater loin eye area and showed a higher meat weight and content of carcass than animals of both EF and FF genotypes (unsignificant association), which suggests that a further study is necessary to confirm or exclude the effect of the POU1F1 gene on these traits.
For 22 carcass traits, we identified 16 QTLs (based on data for pig resource population no. 214, including 180 F2 hybrids of 3 Yorkshire boars and 8 Meishan sows) and mapped them with the use of 39 microsatellite marker loci on chromosomes 4, 6, 7, 8 and 13. Five QTLs were highly significant (P 0.01 at chromosome level): for skin weight (on chromosome 7 at SW1856 and on chromosome 13 at SW1495), skin percentage (on chromosome 7 between SW2155 and SW1856 and on chromosome 13 between SW1495 and SW520), and ratio of leg and butt to carcass (on chromosome 4 at SW1996). The remaining 11 QTLs were significant (P 0.05 at chromosome level): for backfat thickness at shoulder, loin eye width, loin eye height, fat meat weight, lean meat weight, skin weight, bone weight, skin percentage, fat meat percentage, and ratio of lean meat to fat meat. The proportion of phenotypic variance explained by these QTLs ranged from 0.06% (QTL for loin eye width on chromosome 8 between SW1037 and SW1953) to 18.04% (QTL for ratio of lean meat to fat meat on chromosome 7 between SW252 and SW581). Seven of the QTLs reported here are novel.
. The genotypes of growth hormone gene polymorphisms (GH-DdeI, GH-MspI, GH-HaeII, GH-ApaI, GH-CfoI) were determined in 78 pigs [Czech Large White sires (CLWsire line) ? Polish Large White (PLW) sows, Polish Large White sires ? Polish Large White sows], by the PCR-RFLP method. Preliminary studies found only GH DdeI polymorphism to be associated with performance traits. The associations of this polymorphism with growth and carcass traits were investigated. The linear model included the effects of candidate genes, genetic groups, sex and linear covariables of age at slaughter and body weight at weaning. The DdeI polymorphism of the GH gene showed associations with carcass length (P 0.05), average daily gain from birth to weaning (P 0.05) and average daily gain from weaning to slaughter (P 0.05). The association of GH genotypes with feed conversion was near significance. Sex influenced average daily gain from birth to weaning. The genetic groups (Czech or Polish sires) improved fat thickness at sacrum point 3, average daily gain from birth to weaning, lean meat content, weight of chop, weight of shoulder, weight of neck and average daily gain from weaning to slaughter. The regression on age at slaughter and on body weight at weaning influenced the majority of production traits.
MYOG and MYF6 belong to the MyoD gene family. They code for the bHLH transcription factors playing a key role in later stages of myogenesis: differentiation and maturation of myotubes. Three SNPs in porcine MYF6 and two in porcine MYOG were analysed in order to establish associations with chosen carcass quality and growth rate traits in Polish Landrace, Polish Large White and line 990 sows. No statistically significant effect of SNP in the promoter region of the MYF6 gene on its expression measured on mRNA level was found. Associations between the genotype at the MYF6 locus and carcass quality traits appeared to be breed-dependent. The C allele in the case of SNP in the promoter region and GC haplotype in exon 1 were advantageous for right carcass side weight in Polish Landrace sows and disadvantageous for this trait in Polish Large White sows. These gene variants were also the most advantageous for loin and ham weight in sows of line 990. The mutation in exon 1 of the MYOG gene had no statistically significant association with carcass quality traits and the mutation in the 3'-flanking region had the breed-dependent effect as well. These results suggest that SNPs analysed in this study are not causative mutations, but can be considered as markers of some other, still unrevealed genetic polymorphism that influences the physiological processes and phenotypic traits considered in this study.
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