An Approach to Determine the Relationships among Breed Composition, Skeletal Muscle Properties and Carcass Quantitative Traits

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Abstract
Breed composition effects on blood creatine kinase (CK), longissimus muscle transverse area, percentage ham plus loin and postmortem longissimus characteristics were studied by crossbreeding between contrasting purebreds. The experiment utilized pigs of Pietrain (P), which are lean, muscular and a high percentage of which are stress susceptible, and Minn. No. 1 (M), which have the opposite characteristics, and seven cross-bred groups. Resulting composition for the 62 barrows ranged from 100% P to 0% P in 12.5% increments. At approximately 60 kg live weight pigs were subjected to heat stress (10 min, 43 C). Ear-blood samples were taken immediately prior to and following stress and 2- and 24-hr following stress. Blood CK was determined by the luciferin-luciferase procedure. Pigs were sacrificed at 90 kg live weight. No significant differences were noted among breed groups for blood CK prior to and 24 hr after stress. Purebred M displayed the highest CK immediately after stress (840 light units); purebred P the highest CK 2 hr after stress (2,650 light units). CK 2 hr after stress tended to increase with increasing percentage P in the genotype. Longissimus muscle color, structure, marbling and 20-min postmortem pH generally tended to decrease as percentage P in the genotype increased. Longissimus muscle transverse area and percentage ham plus loin increased as percentage P increased. Important exceptions were noted, however, as the 87.5% P group exhibited normal values (close to 0% P) for 20-min postmortem pH, color, structure, marbling and solubility, yet also displayed longissimus muscle area and percentage ham plus loin nearly equal to 100% P. Blood CK screened animals which exhibited low (<6.0) 20 min postmortem pH; such animals exceeded log CK = 2.9. Copyright © 1977. American Society of Animal Science . Copyright 1977 by American Society of Animal Science.