Effect of Age and Sex on Histomorphometrical Characteristics of Two Muscles of Laticauda Lambs

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. Birth type, postnatal development, lamb, histochemistry, nutrition, muscle fibres The Laticauda originated probably from the Northern African sheep, Berbera or Barbaresca, and it got the present characteristics thanks to subsequent crossbreeds with the sheep from the Apennines, the typical one from Southern Italy. Particularly, Laticauda is bred in the country of Benevento and Avellino and during the last years the head number has increased. This breed is traditionally reared in hilly farm pasture predominantly in sedentary breeding groups and the most common farming system is the “family farm type”. Laticauda is a dual-purpose breed with the ability to produce good amount of milk and meat. Meat quality is affected by numerous factors including the growth stage and differentiation of skeletal muscle fibre types. The physiological differentiation of muscle fibres is a dynamic equilibrium which can vary during growth or as a response to the muscle work rate. Guth and Yellin (1971) noticed that muscle fibres continuously change during the animal’s life as a functional demand adaptation and that the fibre type only reflects the fibre constitution at a certain moment. Henkel (1991) suggested muscle histochemistry as a tool for quantifying the effect of different treatments on the size of muscle fibres. In this study we have defined the skeletal muscle fibre populations of lambs by using different methods of m-ATPase and we have analyzed the postnatal development of these fibre populations between 60 and 120 days of age. Muscle fibre type may be classified based on the enzymatic activity; in this study the following nomenclature is used for myofibre types: