Twenty-four pregnant Nellore cows were randomly assigned into 2 feeding level groups (control [CTL]; fed 1.0 times the maintenance requirement; n = 12; and overnourished [ON]; fed at 1.5 times the maintenance requirement; n = 12) to evaluate effects of maternal
overnutrition on fetal skeletal muscle development. Cows were slaughtered at 135, 190, and 240 d of gestation and samples of fetal LM were collected for analysis of
mRNA expression analysis and for histological evaluation of
collagen content and number of muscle cells. There was no interaction between gestational period and maternal nutrition for the variables evaluated (P > 0.05). The
mRNA expression of
Cadherin-associated
protein, β 1 (β-
catenin) tended to be greater in fetuses from ON cows (P = 0.08), while myogenic differentiation 1 (MyoD; P = 0.56),
myogenin (MyoG; P = 0.70), and the number of muscle cells (P = 0.90) were not affected by maternal
overnutrition. Gestational period did not affect the
mRNA expression of β-
catenin (P = 0.60) and MyoG (P = 0.21). The
mRNA expression of MyoD tended to increase with days of gestation (P = 0.06). The
mRNA expression of zinc finger
protein 423 (Zfp423; P < 0.0001), C/EBPα (P = 0.01), and PPARγ (P < 0.0001) were enhanced in ON fetuses. No effects of days of gestation were observed for
mRNA expression of Zfp423 (P = 0.75) and C/EBPα (P = 0.48). The
mRNA expression of PPARγ in fetuses at 190 d of gestation tended to be greater than those at 135 and 240 d of gestation (P = 0.06). The
mRNA expression of
transforming growth factor β (TGF-β; P < 0.0001),
collagen type III, α I (COL3A1; P < 0.0001), and
collagen content (P = 0.01) were increased in ON fetuses. Gestational period did not affect the
mRNA expression of
collagen type I, α I (COL1A1; P = 0.65). The
mRNA expression of COL3A1 (P = 0.09) in fetuses at 190 d of gestation tended to be greater than fetuses at 135 and 240 d of gestation. The
mRNA expression of TGF-β in fetuses at 190 d of gestation was greater than in fetuses at 135 d of gestation (P = 0.03), and the values observed in fetuses at 240 d of gestation did not differ from the other gestational time points. The least value of
collagen content (P = 0.01) was observed in fetuses at 135 d of gestation, and no differences were observed among the other gestational time points. These data shows that maternal
overnutrition enhances fibrogenesis and likely adipogenesis without compromising myogenesis in fetal skeletal muscle of cattle.