Chapter 4 - Muscle growth and development and relationships to meat quality and composition

Abstract

Muscle growth is the result of protein synthesis, and the rate of muscle growth slows as the animal reaches approximately half its mature size. Muscles contain a mixture of three types of muscle fibers: Type I (red), Type II β (white), and Type II α (intermediate). Red muscle fibers are used for sustained work, such as long-term locomotion, and are termed aerobic because they derive their energy from oxidative metabolism. White muscle fibers are larger in diameter than red fibers, are used for short-term, rapid bursts of activity such as quick movement, and are termed anaerobic because they derive their energy from the metabolism of glycogen. Intermediate muscle fibers utilize both oxygen and glycogen to generate ATP for muscle contraction. Selection for animals with larger muscles results in animals having a larger proportion of white and intermediate-type muscle fibers.