Carcass traits, muscle characteristics, and palatability attributes of lambs expressing the callipyge phenotype

Dorset x Suffolk crossbred wethers expressing a normal phenotype (normal, n = 10) and callipyge phenotype (CLPG, n = 9) were fed individually and slau ghtered upon reaching maximum growth potential. Carcass weight did not diff er (P > 0.05), but fat thickness was lower (0.30 vs. 0.56 cm), ribeye area was greater (24.4 vs. 16.6 cm(2)), and USDA yield grade was improved (1.6 v s. 2.6) for CLPG carcasses (P < 0.05). Carcasses from CLPG demonstrated hig her cutability and a more desirable muscle to bone ratio, with less fat and more lean as a percentage of total side weight (P < 0.05). Biceps femoris (BF), semitendinosus (ST), semimembranosus (SM), longissimus thoracis et lu mborum (LTL), and triceps brachii (TB) were used to compare muscle characte ristics of both phenotypes. Muscle from normal lambs had lower calpastatin activity, higher fat percentages and lower moisture percentages (P < 0.05). Total amount and solubility of collagen were not affected by phenotype nor was sarcomere length. Shear force and trained sensory attributes were eval uated for BF and LTL only. Shear force values did not differ between normal and CLPG BF while CLPG LTL had higher (P < 0.05) shear force values than n ormal LTL. Biceps femoris did not differ between phenotypes in trained sens ory panel ratings. However, CLPG LTL received the lowest sensory ratings fo r connective tissue amount and myofibrillar and overall tenderness (6.11, 4 .97, and 4.95, respectively) and the normal LTL received the highest rating s (P < 0.05; 7.10, 7.00, and 6.90, respectively). The CLPG phenotype had a positive influence on carcass characteristics but had a negative influence on tenderness of some muscles, possibly through the myofibrillar component of the muscle. (C) 2001 Elsevier Science Ltd. Al rights reserved.