Prenatal Development of Muscle and Adipose and Connective Tissues and Its Impact on Meat Quality

The abundance of intramuscular fat (marbling) and tenderness are 2 key determining factors of beef quality,whereas muscle growth determines the meat production efficiency. Marbling accumulation is due to both hyperplasia and hypertrophy of intramuscular fat cells (adipocytes). On the other hand, intramuscular fibroblasts are major contributors for the formation of connective tissue and its cross-linking, which are responsible for background toughness of beef.Interestingly, muscle cells, adipocytes, and fibroblasts are derived from a common pool of mesenchymal progenitors during embryonic development. In the early embryos, a portion of progenitor cells in anlage commit to the myogenic lineage,whereas nonmyogenic cells become adipo-fibrogenic cells or other cells. These myogenic cells proliferate extensively and further develop into primary and secondary muscle fibers and satellite cells, whereas adipo-fibrogenic cells form the stromal-vascular fraction of muscle where intramuscular adipocytes and fibroblasts reside. Strengthening prenatal myogenesis and muscle development enhances lean growth, whereas promoting intramuscular adipocyte formation elevates marbling. Because the abundance of progenitor cells in animals declines as their development progresses, it is more effective to manipulate progenitor cell differentiation during early development. Maternal nutrition and other environmental factors affect progenitor cell commitment, proliferation, and differentiation, which programs muscle growth and marbling fat development of offspring, affecting the quantity and quality of meat production.