Histometabolic properties of some skeletal muscles in crossbred lambs of Croatian dairy sheep

Diameters and types of muscle fibers were studied on the basis of histochem ical activity of lactic (LD) and succinic (SD) dehydrogenase and myosin ade nosine triphosphatase (ATP-ase) at pH 4.3 in in. gluteobiceps, in. longissi mus lumborum, nl. psoas major, m. semitendinosus, m. sernimembmnosus, In. q uadriceps femoris (m. rectus femoris) and m, triceps brachii (caput longum) of 9 male lambs originating from the crossbred F-2 between the Istrian Pra menka and Sardinian (S), Domestic Merino-Wurtemberg (W) and East Friesian ( EF) rams 71 days old, weighing 21.74 kg (S), 25.66 kg (W) and 25.43 kg (EF) . Diameter of the fibers and enzymatic activity were different in all inves tigated muscles. The diameter ranged from 10 to 90 mu m (S), 10-85 mu m (W) and 10-70 mu m (EF). The largest average diameter in majority of muscles w as recorded in the S lambs, and the largest number of fibers in the visual field was in the W and EF animals. Glycolytic fibers were the most common, comprising around or over one half of all fibers; oxidative made about one third of all fibers and oxidative-glycolytic were less common than oxidativ e. The slow-twitch fibers accounted for around one third and the fast-twitc h for around two thirds in all investigated muscles. M. longissimus lumboru m, m. semitendinosus, in. semimembranosus and m. quadriceps femoris of the S lambs, then in. gluteobiceps and in. triceps brachii of the W lambs and m . psoas major of the EF lambs contained the most oxidative fibers. Glycolyt ic fibers were mostly in in. longissimus lumborum, m. semitendinosus, m. qu adriceps femoris and m. triceps brachii (W lambs) and in m. gluteobiceps, m , psoas major and in. semimembranosus (S lambs). Majority of the slow-twitc h fibers were in m. semitendinosus, m. semimembranosus, m. quadriceps femor is and m. triceps brachii of the S lambs, in nl. gluteobiceps and m. psoas major of the W lambs and in in, longissimus lumborum of the EF lambs. The m ost of the fast-twitch fibers were in m. gluteobiceps, in. psoas major, m. semimembranosus and in. triceps brachii of the EF lambs, and in. longissimu s lumborum, m. semitendinosus and in. quadriceps femoris of the W lambs. St atistical evaluation shows the significant differences (P < 0.01) in muscle fiber average diameter in each muscle order between all three crossbreds o r only between two crossbreds. The difference in body weight and consequent ly, in meat volume between the S, W and EF animals was also rather due to a larger number of muscle fibers than to the muscle fiber thickness.