Search

The aim of this study was to evaluate the effect of age and sex on histochemical and morphometric characteristics of muscle fibres (myocytes) in lambs born by single or twin birth. Forty lambs were fed mother’s milk and slaughtered at 60 days; 40 weaned at 60 days and fed until 120 days with flakes (60%) and hay (40%) and then slaughtered. Muscle tissues were obtained from two muscles, namely m. psoas major and caput longum m. tricipitis brachii of all lambs. The muscles were stained for myosin ATPase, and succinic dehydrogenase. For each fibre type, area, perimeter, maximum and minimum diameter were measured and slow-twitch oxidative fibres, fast-twitch glycolytic fibres, fast-twitch oxidative-glycolytic fibres were histochemically differentiated. An image-analysing system was used. At 60 days, females had fibres larger than males while the opposite was observed at 120 days. Moreover, at 60 days, the lambs born by single birth had fibres larger than those born by twin birth, while the opposite was observed at 120 days. The fast-twitch glycolytic fibres had the largest size, followed by the slow-twitch oxidative and the fast-twitch oxidative glycolytic fibres. The dimensions of fibre types in caput longum tricipitis brachii muscle were larger than in the psoas major muscle (P < 0.001). This study provides important data on basic characteristics of lamb muscles that, as intrinsic factors, may influence some aspects of meat production and quality.

The aim of the present experiment was to determine the effect of sex and age on histochemical and morphometric characteristics of muscle fibres (myocytes) in lambs born by single, twin, triplet and quadruplet birth. Thirty lambs were slaughtered at 60 days of age; thirty were weaned at 60 days and fed until 120 days with flakes (60%) and food supplements, and then slaughtered. Muscle tissues were obtained from two muscles, namely m. semitendinosus and m. longissimus dorsi of all lambs. For each fibre type, area perimeter and diameter (maximum and minimum) were measured and slow-twitch oxidative fibres, fast-twitch glycolytic fibres, fast-twitch oxidative-glycolytic fibres were histochemically differentiated. The muscles were stained for myosin ATPase, and succinic dehydrogenase. At 60 days, females had fibres larger than males, whereas the opposite was observed at 120 days. Besides, at 60 days, the lambs born by single birth had fibres larger than those born by multiple birth, whereas the opposite was observed at 120 days. Single lambs were heavier than twin lambs and multiple lambs. Fast-twitch glycolytic fibres had the largest size, followed by slow-twitch oxidative and fast-twitch oxidative glycolytic fibres. The dimensions of fibre types in m. longissimus dorsi were larger than in m. semitendinosus (P < 0.001).These muscle fibre characteristics are thought to be important factors influencing meat quality, which is often related to metabolic and contractile properties as determined by the muscle fibre type distribution.

Velotto S., E. Varricchio, M. R. Di Prisco, T. Stasi, A. Crasto: Skeletal Myocyte Types and Vascularity in the Black Sicilian Pig. Acta Vet Brno 2007, 76: 163-170. The objective of this study was to verify the presence of giant fibres in the Black Sicilian pig skeletal muscle and to evaluate the effect of sex on histochemical and morphometric characteristics of the myocytes (myofibres) as well as vascularity of the muscle. Twenty Black Sicilian pigs (10 males, 10 females) from a farm in Sicily (Italy) were slaughtered at two years of age. Muscle tissues were obtained from three muscles: psoas major, longissimus dorsi, and trapezius. Myofibres were stained for myosin ATPase, succinic dehydrogenase, and α-amylase-PAS. For all fibre types, area and perimeter were measured. Slow-twitch oxidative fibres, fast-twitch glycolytic fibres and fast-twitch oxidative-glycolytic fibres were histochemically differentiated; an image-analyzing system was used. The results showed no differences between males and females in percentage of the fibre types, but there were significant differences between sexes in size of all the three fibre types. Psoas major muscle had a high percentage of slow-twitch oxidative fibres and contained more capillaries per fibre and per mm 2 than trapezius and longissimus dorsi, in which fast-twitch glycolytic fibres dominated. The cross-sectional area of all fibres types was larger in longissimus dorsi than in trapezius and psoas major muscles; the giant fibres were absent in all the muscles studied. Fibre type composition may contribute to the variation of meat quality.