The relationships between porcine longissmus dorsi histological traits and carcass and performance characteristics

Twenty-six hogs were raised four to a pen until the average weight per pen was 100 kg. Immediately after slaughter the carcass weight, carcass length and back fat thickness were measured. Following a 14 to 16 hour chill, the weights of the trimmed hams and loins were recorded and converted into percentages. The loin eye at the 10th rib was scored for color and marbling and a one inch chop removed for histological examination. Cross sections (16 microns) were stained for ATPase activity and the muscle fiber types differentiated. Their areas and numbers were recorded and the mean areas and percentages of each fiber type were calcu-lated. The fat cells were stained with Oil-Red-0 and their mean areas calculated. Six of these cross sections for each sample were given a histologically determined marbling score. Simple correlation coefficients were calculated. These showed a relationship between histologically determined marbling and loin eye area (-.49), back fat thickness (0.47) and marbling (0.61). The mean fat cell area was signifi-cantly correlated with loin eye area (-.60), back fat thick-ness (0.55) and marbling (0.52). All the barrows were Durocs and all of the gilts were crossbreeds, therefore any variation between the two groups could not be designated as a result of either sex or breed. The analysis of variance between the Duroc barrows and crossbreed gilts indicated that the mean fat cell area, back fat thickness and marbling score were significantly (P < .01) larger for the Duroc barrows. The crossbreed gilts had significantly (P < ,01) longer hot carcass lengths, higher percent ham and loin and larger loin eye area.