Usefulness of various biochemical and histochemical characteristics as indices of muscle type in lamb carcasses

Contractile and metabolic characteristics of five different muscles from an homogeneous group of seven lambs were studied. Muscle typing was assessed by measuring myofibrillar ATPase and lactate deshydrogenase activities, myosin (FM1, FM2, FM3, SM1, SM2) and LDH (M(4), M(3)H, M(2)H(2), MH(3), H(4)) isoforms levels as well as fibre types composition (SO, SOG, FOG, FG). On this basis, muscles were classified as slow-twitch oxidative (diaphragm and supraspinatus), intermediate (triceps brachii), fast-twitch oxidative-glycolytic (longissimus dorsi) and fast-twitch glycolytic (tensor fascia latae). Discriminant factor analysis of data revealed that variables enabling a better discrimination of muscles (FG, SM1, FM2, FM1, H(4)) exhibited the lowest efficiency to discrimate animals. Furthermore, in contrast to LDH isoforms and fibre type composition subsets of variables, myosin isoforms analysis allowed a quite total identification of muscle classes since, 97·5% of the muscles were well ranged in their respective classes. Although animals were zootechnically similar, animal variability was important and animal effect was essentially detected through changes in the following set of variables: M(3)H, MH(3), SO and ATPase.