Abstract: Skeletal muscle, the most important component of animal body, constitutes 40% of the animal body, while muscle fibers as the primary part of muscle, its differences is one of the critical factors affecting meat quality. Therefore, the growth, development of the skeletal muscles and their physiological and biochemical characteristics will directly affect the meat quantity and quality. Generally, the number of the muscle fibers is fixed during the embryonic development, while the increase of the muscle mass is due to the hypertrophy of skeletal muscle fibers after birth. Moreover, the skeletal muscle fibers types are not completely fixed, the change will be occurred according the metabolism and the functional demand during the growth and development of the skeletal muscle. The biological processes of the skeletal muscle growth and development, and the formation of muscle fibers are quite complex, involving in many genes and signal pathway. With the development of molecular biological technologies, many methods are applied to elucidate the regulatory mechanisms of the formation of many complex biological phenomena. To date, a great progress has been made in study of the molecular mechanisms related to the skeletal muscle development, and many key factors involved in the skeletal muscle growth and development have been identified. In the early study, the researches on the skeletal muscle fibers were focused on the identification of muscle fibers types and their physiological and biochemical characteristics, whereas the studies on the molecular mechanisms are relatively rare. Recently, a breakthrough has been made in the molecular regulatory mechanisms involved in the formation of skeletal muscle fibers. So, it is necessary to completely review the types and properties of muscle fiber, molecular regulatory mechanisms and the relationship between the muscle fibers types and meat quality. In this review, the types and properties of muscle fiber are summarized firstly. Then, the research progress in molecular regulatory mechanisms of the slow and fast muscle fibers formation was presented, respectively. Finally, the relationship of muscle fibers and meat quality was discussed. In general, this review will be helpful for further understanding the genetic mechanisms of the formation of skeletal muscle fiber types, and could be a reference for further studying on the formation of muscle fibers in the future. Meanwhile, the review is able to provide useful information for revealing the molecular mechanisms of meat quality, and provide molecular theoretical evidences for cultivating new breeds or lines using biotechnology in the future.

Key words: agricultural animal , muscle fiber , regulatory mechanism , meat quality