Differences in muscle fibre composition and tenderness of m. longissimus lumborum between heterozygous and homozygous negative Polish Landrace pigs for the RYR1

The objective of this study was to investigate the effect of RYR1 genotype on muscle fibre traits and meat tenderness of m. longissimus lumborum in fatteners. The study was carried out on 16 heterozygous Nn and 24 RYR1-free NN Polish Landrace gilts. Muscle samples were taken to categorize muscle fibre types (I, IIA and IIB) according to their mATP-ase activity and to determine the following technological parameters of meat: hardness and Warner-Bratzler shear force. Muscle fibre percentage, diameter and phenotypic correlation between muscle fibre traits and meat tenderness were estimated. The results obtained indicated that RYR1 genotype had no effect on muscle fibre proportion, meat hardness and shear force. On the other hand, significant differences between groups were found in the size of muscle fibres. The m. longissimus lumborum of the Nn fatteners had significantly larger diameter of all examined muscle fibre types than muscle from group NN. The phenotypic correlations between histological and meat quality traits were generally low. A positive correlation was found between hardness and shear force and percentage of type IIB fibres, in contrast to a negative correlation between hardness and shear force and percentage of type I fibres. On the other hand, size of type I fibres, unlike that of type IIB fibres, positively correlates with meat quality traits. In addition, correlations between fibre type percentages were negative, in contrast to positive correlations between fibre type diameters.