Univ. of Wyoming scientists conducted a study to evaluate the effect of nutrient restriction on muscle development in bovine fetuses. Twenty Angus x Gelbvieh cross cows carrying female fetuses were allotted to one of two dietary treatments from day 39 to day 125 of gestation: 1) Control, fed to gain wt. (avg. +4.25% of body wt.); 2) Nutrient restricted (NR), fed to lose wt. (avg. -6.9% of body wt.). On day 125, half of the Control and NR cows were slaughtered, and the remaining NR cows were realimented to achieve body wt. similar to the remaining Control cows when slaughtered on day 250 of gestation. Upon slaughter at days 125 and 250, the loin muscle of fetuses at the 12th rib was removed and examined for number of myofibers (microscopic muscle fibers).

At day 125, nutrient restriction significantly (P<.05) reduced the avg. number of myofibers in muscle bundles of fetal loin muscle (10.2 vs. 12.2 for NR and Control, respectively). At day 250, the number of myofibers in NR fetuses was still significantly reduced compared to Control fetuses. These results showed that the reduction in muscle fibers due to nutrient restriction in early gestation could not be recovered by realimentation during a late stage of gestation. The authors concluded that the reduced number of myofibers in fetal muscle due to nutrient restriction during early gestation is expected to impact the physiological function of muscle and affect meat quality of progeny (Du et al. 2005. J. Anim. Sci [Suppl. 1]: Abstract 684).