In utero manipulation of muscle development in beef cattle fetuses

Abstract Text: Fetal programming has been suggested as new tool in the current meat industry to produce animals with a potential to produce high quality beef. Such hypothesis is based on the fact that the main cells that compose the skeletal muscle tissue (myocytes, adipocytes, and fibroblasts) are all derived from a common pool of mesenchymal stem cells and their commitment to one of those lineages can be altered, among other factors, by maternal nutrition during the gestational period. Besides myogenesis and adipogenesis, fibrogenesis is very active during the fetal stage, during which generates connective tissue. The presence of connective tissue, primarily in the form of collagen fibrils contributes to the background toughness of meat. Therefore, we investigated the effect of maternal nutrition on molecular mechanisms governing the early commitment of mesenchymal stem cells to either myogenic or adipogenic-fibrogenic lineages in beef cattle fetuses. Twenty-three Nellore pregnant cows were randomly assigned into two feeding level groups where 12 cows were fed at 1.0 times the maintenance requirement (Control - C) and 11 cows were fed at 1.5 times the maintenance requirement (Obese - OB) to evaluate effects of maternal obesity on fetal skeletal muscle development. The mRNA expression of β-catenin (P = 0.0844), MyoD (P = 0.5623), myogenin (P = 0.7048), and the number of muscle cells (P = 0.9032) was not affected by maternal obesity. Conversely, mRNA expression of adipogenic markers ZfP423 (P < .0001), C/EBPα (P = 0.0004), and PPARγ (P < .0001) was enhanced by maternal obesity. Indeed, mRNA expression of fibrogenic markers TGFβ (P < .0001), collagen III (P < .0001), and collagen content (P = 0032) was enhanced in OB fetuses. These data shows that maternal obesity enhances fibrogenesis and likely adipogenesis without compromise myogenesis in fetal skeletal muscle of cattle.

Keywords: Development, muscle, Nellore