Over the last twenty years, pig breeding has been very successful in the selection for improved lean meat production and reduced fat level. In order to meet increasing pressure to reduce fatness and increase muscularity in fatteners different types of meat boars are used by pig producers instead of traditional sires (Landrace, Large White or Duroc). There is some concern that meat and eating quality have suffered as a result of this strong use of meat boars. According to Warriss (2000), specifically the presence of Pietrain genes in many meat-line boars could potentially make their offspring more prone to the production PSE meat. Colour is the major determinant of appearance of raw meat. It can be determined by two main factors – the first is the concentration of the haem pigments, myoglobin and haemoglobin - the second is the muscle microstructure. Heavier slaughter weights have become a feature of a number of markets. Therefore, the objective of this work was to study the effect of sire genotype on the histochemical profile of the M. longissimus dorsi from pigs slaughtered at a relatively heavy weight the 129.3 kg.