Published online by Cambridge University Press: 02 September 2010
Samples from a dark red area of the vastus medialis muscle were taken from eight Canadian Yorkshire-breed pigs after slaughter. Frozen transverse sections were tested for alkali-stable adenosine triphosphatase (ATPase) and the ratio of strong to weak reacting muscle fibres was determined from photomicrographs. The percentage of fibres with strong ATPase reactions was positively correlated (r = 0·82, P<0·01) with animal live weight. This growth-related change is in the opposite direction to that known to occur in the white longissimus dorsi muscle of the pork carcass.