Abstract
Abstract. The aim of the study was to evaluate the association between the microstructure characteristics of longissimus lumborum (LL) muscle and the genotype at porcine loci MSTN and CAST. The study was carried out on 132 unrelated pigs – 93 crosses of Pietrain and (Polish Large White x Polish Landrace) and 39 Stamboek castrated males. Crosses Pi x (PLW x PL), with an equal proportion of castrated males (n=46) and females (n=47), were of genotype CC or CT at the locus RYR1, whereas Stamboek pigs were of genotype CC at this locus. The diameters of slow-twitch oxidative (STO), fast-twitch oxidative (FTO) and fast-twitch glycolytic (FTG) fibers, their per cent share in a bundle and number of fibers per 1 mm2 were determined. Moreover, the analyses covered the frequency of occurrence of pathological fibers, including giant and angular fibers. The parameters examined, characterising the microstructure of LL muscle, were not found to be related to the presence of the C→T polymorphism in exon 3 of the MSTN gene, identified by enzyme TaqI. However, it was shown that the diameters of the STO, FTO and FTG fibres in the LL muscle were significantly smallest in the Stamboek pigs with genotype FF at locus CAST compared to both the remaining genotypes. Among the crosses Pi x (PLW x PL) this genotype was not observed. The content of FTG fibres in a bundle proved to be related to the CAST genotype in Stamboek pigs. The frequency of pathological fibres in the LL muscle was the lowest in pigs with genotype EE at the locus CAST, but only in the case of the crosses Pi x (PLW x PL) was this relation statistically significant. The studies should be continued to determine whether such relations occur in other pig breeds. The frequency of pathological fibres affects meat quality and thus the polymorphism of the CAST gene could be of importance in selection.
Highlights
The skeletal muscle is a tissue of major economic importance for meat production, what in turn means that meat production capacity is related to the number of muscle fibers and their growth rate
The microstructure characteristics of the longissimus lumborum muscle was determined on a total of 132 unrelated pigs: 93 porkers (46 castrated males and 47 females) being crosses of Pietrain and (Polish Large White x Polish Landrace) [Pi x (PLW x PL)] and 39 Stamboek pigs
The mean diameter of slow-twitch oxidative (STO), fast-twitch oxidative (FTO) and fast-twitch glycolytic (FTG) fibers in m. longissimus lumborum, as identified in this study, was comparable to values found by other authors for the same muscle, it is necessary to emphasize that different pig breeds and muscle sampling methods were used (SOSNICKI, 1987)
Summary
The skeletal muscle is a tissue of major economic importance for meat production, what in turn means that meat production capacity is related to the number of muscle fibers and their growth rate. The genetic variability and heritability of muscle fiber number and size is sufficiently high to include these traits in selection, beside the commonly used criteria for improving lean meat content and meat quality (REHFELDT et al, 2000) These traits, as all quantitative traits, are most probably polygenic and affected by non-genetic environmental factors. Myostatin is a member of the TGFβ superfamily of growth and differentiation factors and plays an important role in controlling the development of skeletal muscles as a negative regulator during muscle growth (MCPHERRON et al, 1997). It affects meat quality in cattle (KOBOLÁK and GÓCZA, 2002). BARNOY et al (1996) reported that the fusion of rat L8 line myoblasts was accompanied by a dramatic change in the calpain/calpastatin ratio
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