MEAT SCIENCE AND MUSCLE BIOLOGY SYMPOSIUM: Manipulating mesenchymal progenitor cell differentiation to optimize performance and carcass value of beef cattle1,2

Abstract

Beef cattle are raised for their lean tissue, and excessive fat accumulation accounts for large amounts of waste. On the other hand, intramuscular fat or marbling is essential for the palatability of beef. In addition, tender beef is demanded by consumers, and connective tissue contributes to the background toughness of beef. Recent studies show that myocytes, adipocytes, and fibroblasts are all derived from a common pool of progenitor cells during embryonic development. It appears that during early embryogenesis, multipotent mesenchymal stem cells first diverge into either myogenic or adipogenic-fibrogenic lineages; myogenic progenitor cells further develop into muscle fibers and satellite cells whereas adipogenic-fibrogenic lineage cells develop into the stromal-vascular fraction of skeletal muscle where reside adipocytes, fibroblasts, and resident fibro-adipogenic progenitor cells (the counterpart of satellite cells). Strengthening myogenesis (i.e., formation of muscle cells) enhances lean growth, promoting intramuscular adipogenesis (i.e., formation of fat cells) increases marbling, and reducing intramuscular fibrogenesis (i.e., formation of fibroblasts and synthesis of connective tissue) improves overall tenderness of beef. Because the abundance of progenitor cells declines as animals age, it is more effective to manipulate progenitor cell differentiation at an early developmental stage. Nutritional, environmental, and genetic factors shape progenitor cell differentiation; however, up to now, our knowledge regarding mechanisms governing progenitor cell differentiation remains rudimentary. In summary, altering mesenchymal progenitor cell differentiation through nutritional management of cows, or fetal programming, is a promising method to improve cattle performance and carcass value.

Postweaning substitution of grazed forage with a high-energy concentrate has variable long-term effects on subcutaneous fat and marbling in Bos taurus genotypes1

“…Within pasture-based nutritional systems similar to the present study, neither birth weight or varying maternal nutrition at pasture during pregnancy affected rib fat depth, P8 rump fat depths, MSA marbling score, or LM IMF content in Bos taurus cattle at heavy market weights (380 kg average carcass weight; Greenwood et al, 2006;Greenwood and Cafe, 2007;Robinson et al, 2013). These findings are at odds with the suggestion, based largely on more mechanistic evidence within fetal life and in species other than cattle, that nutrition during gestation may alter fatness and marbling at market weights (Du et al, 2013). In contrast, better maternal nutrition from birth to weaning within pasture-based systems resulted in more rapid growth of offspring and a small but persistent increase in carcass fatness, but not in marbling (Greenwood et al, 2006Robinson et al, 2013), consistent with lack of effect of initial BW (which is indicative of growth and nutrition to weaning) on marbling score or on IMF content of the 5 muscles in the present study.…”

Nutrigenomic regulation of adipose tissue development — role of retinoic acid: A review

“…Due to the low value of visceral and subcutaneous fat, meat animals have been selected for generations for their high lean/fat ratio, resulting in lean animals. However, the selection for high lean growth is negatively associated with intramuscular fat accumulation, or marbling, which is critical for the palatability of meat (Du et al, 2013a; Hausman, Basu, Du, Fernyhough-Culver, & Dodson, 2014; Kauffman, Carpenter, Bray, & Hoekstra, 1964). The use of implants and harvesting at increasingly younger ages are also contributing factors to the low marbling in beef cattle.…”

Fetal programming in meat production

“…2. More detailed information is available in our previous publications (Du et al, 2010;Du et al, 2013).…”