The aim of the study was to evaluate causes of variations in the meat quality of pigs of the (Danish Landrace x Yorkshire) x Duroc [(LxY)xD] breed slaughtered at two different dates. Experiments were carried out on 36 pigs slaughtered in two groups of 18 animals each. The meat quality of the examined fatteners was evaluated on the basis of the analysis of the following parameters: pH value, electrical conductivity, changes of some selected proteins of washed myofibril fractions as well as its tenderness and water holding capacity. It was found that, even though the meat was characterised by normal quality, significant (p≤0.05) differences were observed in the examined parameters (pH measurements 48 and 144 h after slaughter, electrical conductivity 35 min and 3 h after slaughter, centrifugal and thermal drip, shear force and the share of titin degradation product T2 in the fraction of washed myofibrils, the share of MHC 2a isoform in the muscle tissue) between the compared groups of pigs. The observed variations in the muscle quality could have been caused by metabolic properties of muscle tissues as indicated by the proportion of the 2a myosin heavy chain (MHC) isoform as well as by different growth rates of experimental animals.